LABQF2020 - moodle.up.pt · Ana Filipa Reis Gomes #14 | Speciation in acid-base equilibrium pg. 065...

LABQF2020LABORATORY OF PHYSICAL CHEMISTRY

DQB... 2019-2020UC Q2006:PHYSCHEMlab

Students Slide Book | 2020

Note/Alert: The content of the slides was discussed but not edited nor corrected.The content of this Slide Book is only intended for internal use and cannot be commercialized nor used for other purposes.Some slides may have serious inaccuracies or type mistakes.

Teaching staff: Luís Belchior Santos; Ana Lobo Ferreira; Carlos Lima

LabQF2020 _ Students Slide Book | 2020 Pg # 2

Index: #01 | Solid-liquid equilibrium of binary mixtures pg. 004

Catarina Nogueira Dias

#02 | Combustion bomb calorimetry pg. 010

Joana Paz Vieira

#03 | Mechanisms of chemical reactions pg. 015

João Manuel Pires Vieira

#04 | Vapour pressure equilibrium of pure compounds pg. 020

Matilde Santos Barbosa

#05 | Equation of state of pure compounds pg. 025

Daniela Alexandra Santos Pereira

#06 | Ionization equilibrium of a diprotic acid pg. 030

Gabriela Martins Werdan

#07 | Ionic conductivity of an electrolyte solution pg. 035

Nuno Alexandre Sousa Dias

#08 | Debye-Hückel equation pg. 040

Sara Raquel Domingues Figueiredo

#10 | Eutectic composition in SLE pg. 045

Hugo Filipe Costa Almeida

#11 | Rate law of chemical reactions pg. 050

João Miguel de Sousa Almeida Bello

#12 | pH measurements and pH scale pg. 055

Mariana Salomé Nunes da Cunha

#13 | Conductivity measurement of an electrolyte solution pg. 060

Ana Filipa Reis Gomes

#14 | Speciation in acid-base equilibrium pg. 065

Carolina Gonçalves Lourenço

#15 | Integrated Clausius Clapeyron equation pg. 070

Francisco Diogo Moreira Alves

#16 | Non-ideal solid-liquid equilibrium pg. 075

Inês Carolina de Vasconcelos Mendes

#17 | Phase diagram of pure compounds pg. 080

Ana Isabel Fernandes Moreira

#18 | Energy and enthalpy of combustion pg. 085

Joana Margarida Ribeiro da Silva

#19 | Chemical equilibrium pg. 090

Lia Pereira da Costa

#20 | Enthalpy and entropy of vaporization pg. 095

Luiza Helena Duarte Fernandes

#21 | Equation of state of an ideal gas pg. 100

Cristiana Filipa da Costa Oliveira

#22 | Ionization equilibrium of a monoprotic acid pg. 105

Juliana Esteves Martins

#23 | Temperature dependence of the ionic conductivity pg. 110

Mariana Arantes Azevedo

#24 | Extended Debye-Hückel equation pg. 116

André Filipe Sousa Rodrigues

#25 | Temperature dependence of the heat capacity pg. 121

Filipa Leça Santos

#26 | Solid-solid transition pg. 126

Mariana Lopes Damas Carvalho

#27 | Dynamic equilibrium of a chemical reaction pg. 131

André Sousa Santos

#28 | Conductivity measurements of electrolyte solutions pg. 136

Catarina Esteves da Silva Batista Ferreira

#29 | Isomerization effect in the vaporization of alcohols pg. 141

Beatriz Alves da Rocha

#30 | Phase transition equilibrium pg. 146

Inês de Almeida Marques

#31 | Inter and intra molecular interactions pg. 151

José Carlos Cortês Mesquita

LabQF2020 _ Students Slide Book | 2020 Pg # 3

Index: #32 | Critical point & supercritical fluid pg. 156

Ana Isabel da Costa Campinho

#33 | Speciation in the ionization equilibrium of a diprotic acid pg. 161

Edite Ferreira Pinto

#34 | Concentration dependence of the ionic conductivity pg. 166

Inês Maria Manso Santos

#35 | Triple point in a phase diagram pg. 171

Ricardo Emanuel da Costa Moreira

#36 | Gas phase heat capacity pg. 176

Ana Teresa Gonçalves e Silva

#37 | Undercooled liquids pg. 181

Inês Filipa Cabral Real Libânio

#38 | Temperature dependence of chemical equilibrium pg. 186

Joana Patrícia Ferreira Teixeira

#39 | Glass transition phenomenon pg. 191

José Miguel Silva Ferraz

#40 | Phase separation in binary mixtures pg. 196

Ana Margarida Gomes Moreira Alves

#41 | Phase rule pg. 201

Bárbara Neiva Sampaio

#42 | Temperature dependence of physical processes pg. 206

Fátima Daniela Aguiar Gonçalves

#43 | Solutions of weak electrolytes pg. 211

Mariana Silva Almeida


DQB... 2019-2020

Solid-liquid Equilibrium of Binary Mixtures

Catarina Dias

PHYSCHEMlab_Topic#01

Solid-liquid Equilibrium of Binary Mixtures Slide # 2

Eutectic

TemperatureComposition PointSystem

Types of systems:

- Ideal behavior (or almost ideal behavior)

- Non-ideal behavior

Experimental values of the eutectic temperature show little deviation from the literature values

Types of solid-liquid mixtures:

- Miscible or immiscible liquids- Miscible or immiscible solids

Any binary mixture with immisciblity in the liquid phase and miscibility in the liquid phase shows eutectic behavior.


Liquidus

Solidus

e

Separates the field of all liquid from that of liquid+solid

Separates the field of all solid from that of liquid+solid

Schöeder-Van Laar equation:

Eutectic point – where the maximum number of allowable phases are in equilibrium.


Cooling curves

1) Liquid cooling2) Break- Temperature at which the crystallization begins3) Liquid + solid cooling4) Halt- Region where the temperature is constant for longer periods of time

Mixtures with cooling curves that only have halts have eutectic composition. Eutectic temperature

5) Solid cooling


Examples of almost ideal eutectic behaviour

Bibenzyl-biphenyl Bibenzyl-naphthalene Biphenyl-naphthalene


Deep eutectic solvents

Systems formed from a eutectic mixture of Lewis and Brønsted acids and bases, which can contain a variety of anionic and/or catiotic species.

Hydrogen-bond donor + anion of the Hydrogen-bond acceptor

- Easy to prepare- Widely available

- Biodegradable

- Non-toxic/better for the environment

Replacement for common ionic liquids:

- Cheaper

Urea: - Hydrogen-bond donor

Choline chloride (ChCl):- quaternary ammonium salt

Abbot:


DQB... 2019-2020

Combustion Bomb Calorimetry

JOANA VIEIRA


#02 Combustion Bomb Calorimetry Slide # 2

OPERATION PRINCIPLE

• Combustion Bomb Calorimetry is a device used to measurethe amount of heat involved in a chemical or physicalprocess, through a rise in temperature in the surroundings,into organic compounds.

• Calibration

- Electrical- Chemical

∆∆

∆𝑈∆

= ε

Equation 1 – Amount of heat releasedor absorbed during the reacton

Q = m x c x ∆ઙ

Equation 2- Constant of calibration.

Figure 1 – Isoperibolic Combustion BombCalorimetry

Figure 2 – Scheme of a Calorimeter Bomb that uses water as a calorimetric liquid

• Operation Principle

- Oxygen saturation- Ignition source

http://www.trammit.com.br/linha-cientifica/1089-calorimetros-para-medicao-de-poder-calorifico-de-solidos-ou-liquidos.html

https://www.greelane.com/es/ciencia-tecnolog%C3%ADa-matem%C3%A1ticas/ciencia/coffee-cup-and-bomb-calorimetry-609255/

http://www.trammit.com.br/linha-cientifica/1089-calorimetros-para-medicao-de-poder-calorifico-de-solidos-ou-liquidos.html

https://www.greelane.com/es/ciencia-tecnolog%C3%ADa-matem%C3%A1ticas/ciencia/coffee-cup-and-bomb-calorimetry-609255/


Combustion Bomb Calorimeter Ballistic Combustion Bomb

Figure 3 – Scheme of a Calorimeter Bombthat uses water as a calorimetric liquid

Figure 5 - Ballistic Combustion Bomb

TYPES OF CALORIMETERS

Figure 6- Naphtalene Combustion ReactionFigure 4 - Schematic flow-sheet of the set up of the mini-bomb calorimeter

Mini-Bomb Calorimeter

https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_A_Molecular_Approach_(Tro)/06%3A_Thermochemistry/6.05%3A_Constant_Volume_Calorimetry-_Measuring_%CE%94U_for_Chemical_Reactions

https://www.fc.up.pt/pessoas/lbsantos/Papers/CV/pdf_033.pdf

https://moodle.up.pt/pluginfile.php/3653/course/section/3130/Miller-ballis_balistica%20bomb%20calorimetry.pdf

https://chem.libretexts.org/Bookshelves/General_Chemistry/Map:_A_Molecular_Approach_(Tro)/06:_Thermochemistry/6.05:_Constant_Volume_Calorimetry-_Measuring_%CE%94U_for_Chemical_Reactions


https://moodle.up.pt/pluginfile.php/3653/course/section/3130/Miller-ballis_balistica%20bomb%20calorimetry.pdf

WHAT INFORMATION CAN WE EXTRACT FROM IT ?

Combustion Bomb Calorimetry is used for determining thestandard molar enthalpies of formation in the condensed phase oforganic compounds.

Equation 5 – Variation of combustion enthalpy.


Figure 7 – Experimental Plot of Temperature vs Time in constant-volume calorimeter

Figure 8 - Schematic representation of a typical temperature–time curve in isoperiboltemperature-rise calorimetry

∆Hm = ∆Um + ∆nRT

∆𝑈 q + wEquation 3 – First Law ofThermodynamics

∆𝑈 q

Equation 4 – When the systemis closed and a constantvolume



Figure 10 - Nutritional information presented on the label of the Nestlé NIDO® whole milk powder packaging

EXAMPLE OF AN EXPERIMENTAL DETERMINATION, USING COMBUSTION CALORIMETRY


Figure 9 - Nutritional information presented on the Kellogg´s Corn Flakes® cereal packaging label.

In the food industry, combustion calorimetry is also used to determine the energy value of food

Relevant information: 0,8 % in lipids and 7% in glycids Relevant information: 26,2% in lipids

and 38,6% in glycids

https://www.scielo.br/scielo.php?pid=S0100-40422010000100038&script=sci_arttext&tlng=pt

https://www.scielo.br/scielo.php?pid=S0100-40422010000100038&script=sci_arttext&tlng=pt


DQB... 2019-2020

Mechanism of a chemical reaction

JOÃO VIEIRA

PHYSCHEMlab_topic#03

Mechanism of a chemical reaction Slide # 2

Fig.1: Elementar reaction

Two Step Reaction

Fig3: This is a sample reaction coordinate of a complex reaction.

Reactants→Intermediates→ProductsElementary Reaction (one step)

Reactants→Products

Fig.2: This is a sample reaction coordinate of an elementary reaction.

[What is an elementary reaction?]

Reaction mechanism

• The reaction mechanism describes the sequence of elementary reactions that must occur to go from reactants to products.

NO2(g) + CO(g) → NO(g) + CO2(g)

rate = k · [NO2]2First order

2NO2(g) → NO(g) + NO3(g) Elementary step 1NO3(g) + CO(g) → NO2(g) + CO2(g) Elementary step 2

NO2(g) + CO(g) → NO(g) + CO2(g) Overall reaction

reaction intermediate


Velocity

v = k · [A]a · [B]b

Chemical kinetics is the area of physical chemistry that studiesthe speed of chemical reactions and the factors that influence it

aA + bB → cC + dD

Eq.2 : Equation that represents anychemical reaction

Eq.3: Rate law

Fig.4: Cato Maximilian Guldberg and Peter WaageFactors affecting the rateof the reaction

TemperatureConcentration of reagentesSurface areaPressurePhysical stateNature of the reactantsPresence of a catalyst


Types of Elementary Reactions

The molecularity of a reaction refers to the number of molecules that react in an elementary step. Molecularity can be described as:• unimolecular• bimolecular• termolecularThere are no known elementary reactions involving four or more molecules. Unimolecular Reaction Bimolecular Reaction Termolecular Reaction

Table 1: The three known types of elementary reactionsFig.5: Reaction mechanism - Unimolecular

Molecularity Elementary Step Rate Law ExemplesUnimolecular A → Products rate=k[A] N2O4(g)→2NO2(g)

BimolecularA+A → Products rate=k[A]2 2NOCl→2NO(g)+CO2(g)A+B → Products rate=k[A][B] CO(g)+NO3(g)→NO2(g)+CO2(g)

Termolecular

A+A+A → Products rate=k[A]3

A+A+B → Products rate=k[A]2[B] 2NO(g)+O2(g)→2NO2(g)

A+B+C → Products rate=k[A][B][C] H+O2(g)+M→HO2(g)+M


v = k · [CH3Cl][OH-]

Aplication of case study

bjahhjgjhjdljfhs

velocity

Eq.5: Rate law

Eq.4 : Equation of an chemical reaction

Fig.7: Representation of an reaction mechanism

Fig.8: This is a sample reaction coordinate of an elementary reaction.

Fig.6: Chemical reaction between methane chloride and sodium hydroxide


DQB 2019-2020

Vapour pressure equilibrium of a pure compound

Ma ilde San o Ba bo a


Example Slide # 2

� The vapor pressure (P°) is the pressure of the vapor of a compound in equilibrium with its pure condensed phase (solid or

liquid).

When there is a lid on thecontainer, thegas phasemolecules are trapped theyare a vapor. Thevapor creates a pressure!!

� Lid blocks exiting vapor� Molecules in vapor phase

collide with walls and cause a pressure

- The vapor pressure!!� Evap rate = Condense rate

- An equilibrium!!� Change T, change Evap rate,

change Pvap- Pvap is temperature

dependent

Definition of Vapour Pressure Slide

or meltingpoint

Liquid

Solid Gas

Vaporization curve

Fusion curve

Sublimation curve

slope of the tangent to the coe istence cur e at an point

specific latent heat specific entropy change of the phase transition

specific volume change of the phase transition

C

Factors on which vapour pressure depends Slide # 4

FACTORS ON WHICH VAPOUR PRESSURE DEPENDS

Na e of liq id

Effec of Tempe a e

Uses and curiosities Slide # 5

The International System of Units (SI) recognizes pressure as a derived unit with the dimension of force per area and designates the pascal (Pa) as its standard unit.

I o eni cope


DQB 2019-2020

EQUATION OF STATE OF PURE COMPOUNDS

DANIELA PEREIRA

PHYSCHEMlab_EQUATION OF STATE OF PURE COMPOUNDS#05

EQUATION OF STATE OF PURE COMPOUNDS Slide # 2

Equation of state Pure compound

relates the pressure p, volume V and temperature T of a physically homogeneous systemin the state of thermodynamicequilibrium f(p, V, T) = 0.

compounds consisting of oneand only one type of atom ormolecule.

Example: Water, iron and steel.

example

Fig.1- Molecules of H2O


Van der waals equation

P- pressureV- volume n- amount of substance

R- the gas constantT- temperature

Ideal gases


Example of aplication- cooker pressure


Curiosities

Fig.2- Fridge Fig.3- hot air ballon

Fig.4- gun Fig.5- lungs


DQB... 2019-2020

IONIZATION EQUILIBRIUM OF A DIPROTIC ACID

Gabriela Martins Werdan


Ionization equilibrium of a diprotic acid Slide # 2

What is a diprotic acid?

H2A (aq) ⇌ H+ (aq) + HA-

(aq)

HA-(aq) ⇌ H+

(aq) + A2-(aq)

Ka1 = "#$ ["&]["(#]

Ka2 = #($ ["&]["(#]

Ka1

Ka2

H2S (Hydrogen sulfide) H2SO4 (Sulfuric acid)

H2CO3 (Carbonic acid)

H2C2O4 (Oxalic acid)

H2CrO4 (Chromic acid)

Such as:

Depends on: Le Châtelier’s Principle

Ka1 > Ka2

Kw = Ka x Kb


Some examples

H2SO4 (aq) + H2O (l) ⇌ HSO4-(aq) + H3O+

(aq) (1)

HSO4-(aq) + H2O(l) ⇌ SO4

2-(aq) + H3O+

(aq) (2)

Ka1

Ka2

Ka1 >> Ka2In this case, first

ionization is complete

Strong diprotic acid

Ka1 = 103 (large) Ka2 = 10-2

H2CO3 (aq) + H2O(l) ⇌ H3O+(aq) + HCO−

3 (aq) (1)

HCO−3(aq) + H2O(l) ⇌ H3O+

(aq) + CO32-

(aq) (2)

Ka1 > Ka2We have to consider

first and second ionization

Weak diprotic acid

Ka1 = 4.3x10-7

Ka2 = 4.8x10-11

Ka1

Ka2

pH = pKa + log [#$]

[&#] OR ICE Table

Henderson-Hasselbach equation


Titration curves

Speciation curves


Applications

Respiratoryacidosis

Most biochemical processes à Enzyme activity

Buffer solutions

Comercial applications à Baby lotions, shampoos, contact lens solutions

LABQF2020 LABORATORY OF PHYSICAL CHEMISTRY

DQB... 2019-2020

IONIC CONDUCTIVITY OF AN ELECTROLYTE SOLUTION

Nuno Alexandre Sousa Dias


Ionic Conductivity of an Electrolyte Solution Slide # 2

What is an Electrolyte?

An electrolyte is a substance that produces ions in solution when dissolved in water. When there is a complete ionization of a substance, the electrolyte will be known as a strong electrolyte. If there is only a partial ionization of a substance, then the electrolyte will be called a weak electrolyte.

Nonelectrolyte

A Nonelectrolyte is a substance that does not produce ions in solution.

𝑚kc

k=conductivity c=molar concentration 𝑚=molar conductivity


We distinguish the types of Electrolytes by measuring eletrical conductivity.

In a solution, the free mobile charged species are the ions that result when a substance dissociates.

We can measure the current flow (with a voltmeter) or place a lighbulb and observe its brightness to see what type of Electrolyte the species is.

𝑯𝑪𝒍 𝑯 𝑶 → Cl- + H3O+

Factors that influence conductivity: Æ Ion concentration Æ Temperature Æ Nature of Electrolyte

𝑪𝑯 𝑪𝑶𝑶𝑯 + H2O CH3COO- + H3O+


Application of Electrolytes

Battery: A battery is a device that stores chemical energy and converts it to electrical energy. Æ The chemical reactions in a battery involve the flow of electrons from one material (electrode) to another, through an external circuit. Æ Ions balance the flow of electrons. Æ Electrolytes serves as a catalyst.


Other Applications

Æ Many important chemical and metallurgical products are obtained/refined by eletrochemical processes.

Æ In human physiology, electrolytes are involved in essential processes.

CuSO4

Cu2+ SO42-

SO42- Cu2+ Cu

SO42- Cu2+

← ← ←


DQB... 2019-2020

Debye-Hückel Equation

Sara Raquel Domingues Figueiredo


Debye-Hückel equation Slide # 2

In 1923, Peter Debye and Erich Hückel developed a quantitative theory where they physically interpreted the ionic behavior of any solution containing strong electrolytes. Known as Debye-Hücke's theory, it is based on the theoretical explanation for deviations of ideality in strong electrolyte solutions. Debye and Hückel noted that solutions containing ions do not behave ideally, even at very low concentrations. Thus, although the concentration of solutes is important for calculating the dynamics of a solution, they theorized that an extra factor they mastered with gamma, ࢽ,was necessary to estimate the coefficients of activity of the solution. Therefore, they developed the Debye-Hückel equation.

At solutions electrolytes are completely dissociated into ions. Thus, the main reason for the deviations from the ideality of electrolyte solutions is due to the strong electrostatic interactions between the dissociated ions of the solution. Thus, ions with the same charge signal repel each other, and ions with opposing charge signals attract each other.


Derivation of the Debye-Hückel equation

𝐼12 𝐶𝑖𝑍𝑖2

𝐴𝑖 𝐶𝑖 𝑖 ⇔𝑖

𝐴𝑖𝐶𝑖

𝑙𝑜𝑔 𝑖𝐴𝑧𝑖2 𝐼

1 𝐵𝑎 𝐼

Ionic Strength

𝐶𝑖 – concentration of ion𝑍𝑖 – ion charge

Activity Coefficient

𝐴𝑖 - ion activity𝐶𝑖 - ion concentration

Debye-Hückel equation

𝑎- effective ion hydration radius𝑍𝑖 - ion charge𝐴 and 𝐵 - Constants that depend on a certain temperature (Debye-Hückel constants) 𝐼 – ionic strength


𝑙𝑜𝑔 𝑖 𝐴𝑧𝑖2 𝐼For many ion the product 𝐵𝑎 is very close to 1, and in situations that works with low concentrations, can simplify the Debye-Hückel equation – Debye-Hückel limiting law

For the limiting law to be valid, when the ionic strength of the solution is much higher, the coefficient of activity can be calculated from the Debye-Hückel extended law:

𝑙𝑜𝑔 𝑖𝐴𝑧𝑖2 𝐼1 𝐵 𝐼

Modifications of the Debye-Huckel equation


Effect of ionic strength on the rate of reduction of Hexacyanoferrate(III) by Ascorbic Acid

2[Fe(CN)6]3- + C6H8O6 2 [Fe(CN)6]4- + C6H8O6 + 2H+

Exp 1 Exp 2 Exp 3 Exp 4m/s-1 -5,78x10-4 -6,59x10-4 -8,80x10-4 -1,17x10-3

k/mol-1.dm3.s-1 1,34 1,52 2,03 2,71Log(k) 0,127 0,182 0,307 0,433

I/ mol.dm-3 0,015 0,025 0,055 0,105

Limiting law I1/2/ mol.dm-3 0,122 0,158 0,235 0,324

Extendedlaw

I1/2 /(1+I1/2)/mol.dm-3

0,109 0,137 0,190 0,245

Debye-Hückel limiting law Debye-Hückel extended law

𝑙𝑜𝑔𝑘 𝑙𝑜𝑔𝑘0 2𝐴𝑧𝐴𝑧𝐵 𝐼

𝑙𝑜𝑔𝑘 𝑙𝑜𝑔𝑘02𝐴𝑧𝐴𝑧𝐵 𝐼1 𝐼

Debye-Hückel limiting law Debye-Hückel extended law

ZAZB (expected) ZAZB_I1/2 (experimental)/ mol.dm-3

ZAZB_I1/2 /(1+I1/2) (experimental)/ mol.dm-3

3 1,5 2,2


DQB 2019-2020

Eutectic Composition in Solid-Liquid Equilibrium

Hugo Filipe Costa Almeida


EutecticComposition in Solid-Liquid Equilibirum Slide # 2

Binary Systems and Entropy of Mixing

Equation 1 – Schroeder-Van Laar Equation

Binary System

Mixture of two substances that don't react witheachother and have different melting points.

Both substance's melting point decreases with a ratio given by the Schroeder-van Laar equation.

Entropy of Mixing

A mixture of two miscible substances is associated with an increase in entropy.Since the liquid phase becomes more stabilized compared to the solid, the melting point decreases.

Graphics 1 and 2: increase of entropy of mixing with respect to mole fraction

Graphics 1 and 2: Sergey Yu. Karpov, Natalya I. Podolskaya, Igor A. Zhmakin ( 2004 ) ''Statistical model of ternary group-III nitrides''


Phase Diagrams, Eutectic Point and Eutectic Composition

Phase Diagram and Eutectic Point

The phase diagram gives us the distinct phases of themixture caused by the variation of conditions liketemperature.

Eutectic Point - temperature that corresponds to the lowest melting point of the mixture.

Graphic 3 – Generic phase diagram of a binary system

Graphic 4 – Phase diagram of a binary system ( with components A and B )

Graphic 3 : https://www.e-education.psu.edu/eme812/node/704 Graphic 4 and Equation 2: https://en.wikipedia.org/wiki/Eutectic_system

Eutectic Composition

Below the eutectic point the mixture solidifies like a pureliquid.An eutectic system is an homogeneous mixture of twosubstances forming a super-lattice in the solid state.Therefore, the eutectic composition is the ratio betweencomponents A and B that will form an eutectic system.

Equation 2 - Eutectic reaction withaneutectic ratio

https://en.wikipedia.org/wiki/Eutectic_system


FIgure 2 – Four eutectic structures. A : lamellar ; B : rod-l ike ; C : globular ; D : acicular

Figure 1 – Super-lattice representation

FIgure 1 : https://en.wikipedia.org/wiki/Superlattice and Figure 2 : https://en.wikipedia.org/wiki/Eutectic_system

Eutectic Composition and Eutectic Structure

To get an eutectic composition we need theright binary system ratio.If we have any other ratio we get eitheran hypereutectic or hypoeutectic.

An eutectic system can have many structures, with the most common being the lamellar structure.

https://en.wikipedia.org/wiki/Superlattice

https://en.wikipedia.org/wiki/Eutectic_system


Examples of Eutectic Compositions and Applications

Deep Eutectic Solvents

Systems formed with Lewis or Brønsted acids and bases.Ionic solvents with special properties.These systems have melting points incredibly lower thanthose of its components.

Melting Point: 302 °C Melting Point: 133 °C

DES Melting Point: 12°C

FIgure 5: Choline Chloride and its melting point Figure 6: Urea and its melting point

Figures 3 and 4: SLE experiment with naftalene and biphenyl

Graphic 6: Results of the experiment with naftalene and biphenyl


DQB... 2019-2020

João Miguel de Sousa Almeida Bello


Rate Law of Chemical Reactions

Rate Law of Chemical Reactions Slide # 2

What is the Rate Law of Chemical Reactions?

• The rate law for a chemical reaction is an equation that expresses therelationship of the rate of reaction to the rate constant and the concentrations or pressures of the reactants.

aA + bB ProductsRate = k [A]x[B]y

• The rate constant, k, is a proportionality constant in the relationship between rate and concentrations. It only changes in case there´s an alteration of temperature.

The rate law for a chemical reaction is an equation that expresses the relationship of the rate of reaction to the rate constant and the concentrations or pressures of the reactants. I purpose is

to determine the effect of the concentration of the reactants in the speed.

[A] and [B] express the concentration of the species A and B

Reaction is x order with respect to A

Reaction is y order with respect to B


Reaction Order • The order of reaction with respect to the reactant is the exponent of its concentration in the rate

equation,

Rate = K [A]x[B]y ,

x and y are the orders for each reactant. The order can be 0, 1, 2 or fractions and can only be determined byexperiment.

The Overall Reaction Order• The overall reaction order is the sum of all exponentes of the eac an concentrations,

Overall order = x + y

• When the overall reaction order is zero, Rate = k. This because any number with exponent equal to 0 is 1.


Example of Rate Law and Reaction Order

aA + bB Products

[A] Initial Rate [B] Initial Rate1.00 M 0,01 M/s 1.00 M 0,01 M/s2.00 M 0,02 M/s 2.00 M 0,04 M/s3.00 M 0,03 M/s 3.00 M 0,09 M/s

Rate = K [A]1[B]2

Overall Order = 3

Application in the Real WorldTo determine the age of an ancient artifact is most common to apply the radio carbon dating method and chemical kinetics. Like the exampleof the Holy Shroud of Turin, that for years was unknown if the shroudhad ac all belonged o Je Ch i o no I a hen de e mined iage through the application of radio carbon dating and chemical kinetics.


ConclusõesThe rate law and the reaction order allows us to determined the velocity of a reaction through the concentration orpressure of the reactants, which helps understand better the chemical balance of a reaction. The rate law helps (along with the radio carbon dating method) to determine the age of carbon isotopes and otherelements. But most importantly it is very used in the chemical industry to figure out the fastest ways in the production ofchemicals for is more important to produce quicker than to produce a lot.


DQB... 2019-2020

pH Measurements and scale

Mariana Salomé Nunes da Cunha


pH measurements and pH scale Slide # 2

pHScale

pHmeasurements

pH measurements:pHmeter

Aplications

• pH means the abbreviation for pondus hydrogeniitranslated as hydrogen potential.

• It was discovered by a biochemist, named SorenSorensen.

• pH scale is a scale of values, and its used to determinethe degree of acidity or basicity of a given substance.

• The lower the pH of a substance, the greater the H+ ionactivity and lower the OH- ion activity

• The pH values depends on temperature.


pHscale

pHmeasurements


Aplications

Acid-base indicators: phenolphthalein, methyl ornage, bromothymol blue.

Universal indicators: mixture ofvarious indicator subtances.Litmus paper: its a practical

method but its not an exactone.

pHmeter: it measures the electrical conductivity of thesolution. It has an scale incorporated graduated in pH

values. It must be calibrated for better results.


pHScale

pHmeasurements


Aplications

Reference electrode – uses an porous junctionbetween the measured liquid and a neutral, stablesolution, pH buffer creating a zero voltage electrical

connection to the liquid.

pH electrode – it creates a smallvoltage proportional to the pH.


pHScale

pHmeasurements


Aplications

Physiological pH: to establish the pH value of a

cosmetic product it isnecessary to know the pH of the region to which the

product will be applied

Destruction of corals: the increase in theacidity of the oceans causes the whitening of

the corals, leading to their destruction.


DQB... 2019-2020

Conductivity measurement of na electrolyte solution

Ana Filipa Reis Gomes


Conductivity measurement of na electrolyte solution Slide # 2

First, it is important to know what an electrolyte solution is.

An electrolyte solucion is a solution that generally contain ions, atoms or

molecules that have lost or gained electrons, and is electrically

conductive. Na+

K+Cl-

Ca2+

Mg2+

Examples of electrolytes

� Conductivity (or specific conductance) of na electrolyte solution is a measureof its ability to conduct eletricity. The SI unit of conductivity is (S/m).

Figure 1 - Comparation of conductivity in different solutions.

What it is ?


What does conductivity depend on ?

o Concentration (usually expressed in mg/L) – The more concentrated a solution is, the higherthe conductivity is.

o Temperature - Generally the conductivity of a solution increases with temperature, as the mobility of the ions also increases.

o Ionic charge – The higher the concentration of dissolved salts, which will lead to more ions, the higher the conductivity.

A strong electrolyte is one where many ions are presente in the solution – strong electrolytes are good conductors of electricity.

Another important point is dilution, in fact, the conductivity of an electrolyte decreases with dilution.

Figure 4 - Graph on which relates conductivity and temperature.


How is conductivity of electrolytes measured ?

9 The electrical conductivity of a solution of na electrolyte is a measure by determinig the resistance of the solucion.

9 It is important to control the temperature during the experiment.

9 It is important to calibrate the appropriate equipment, such as the conductivity meter, with a known concentration of KCl.

What is the principle of conductivity meter?

Figure 2 - Conductivity meter

Figure 3 – Conductivity measurement.

9 Potentiometric method

9 Use of alternating current.

9 Cylindrical electrodes and arranged in parallel.

9 Electrodes usually made of platinum metal.


Conductivity measurements are used to monitor the quality of public water supplies, in hospitals, in industries that depend on water quality (such as brewing).

Why is Conductivity Important?

The specific conductance (conductivity)

Molar conductivity.(S m2 mol-1)

Figure 3 - Principle of the measurement.

Measurement of ionic content.

Conductivity

Specific resistance

Molar conductivity


DQB... 2019-2020

CAROLINA GONÇALVES LOURENÇO


Speciation in an Acid-Base Equilibrium

Speciation in na Acid-Base Equilibrium Slide # 2

Speciation is the process ofdetermining the

equilibrium distribution ofchemical species in

solution.

Acid/Base Equilibrium ? Speciation ?

Type of chemical process typified bythe exchange of one or more hydrogenions, H+, between species that may be

neutral or electrically charged. CH3COOH (aq) H+ + CH3COO- (aq)

What is

Slide # 3

Monoprotic acid, HA, HA H+ + A-

Triprotic acid, H3A, H3A H+ + H2A-

H2A- H+ + HA2-

HA2- H+ + A3-

Speciation in na Acid-Base Equilibrium

Methodologies

Figure 1: System utilized in potenciometric titration

Figure 2: Schematic diagram ofthe coulometric cell

InSlide # 4

SpeciationCalculations

Dissociation of an acid:

H2A H+ + HA-

Relationship between

concentration of acid and pH:

BM: CT = [A2- ]+[HA-] +[H2A] = total concentration of

species A

HA- H+ + A2-

Ka1

Ka2

Equilibrium constant:

Ka1= [H+][HA−]

[H2A]Ka2=

[H+][A2−][HA−]

#0 =[H2A]

CT #1 =[HA−]

CT #2 =[A2−]

CT

#0+ #1+ #2 = 1

= [H+]2

[H+]n+[H+](n−1)Ka1 + [H+](n−2)Ka1Ka2+Ka1Ka2 … Kan

For any system:

#0

Ionic Strength

Solubility

Temperature

Factors thatinfluencespeciation

Ka values

Speciation in na Acid-Base Equilibrium

Speciation in na Acid-Base Equilibrium Slide # 5

Figure 4: Relative speciation (%) of carbondioxide (CO2), bicarbonate (HCO - 3) andcarbonate (CO 2-

3) in water as a function ofpH

CO2 Speciation

CO2 controls thepH of the oceans

Major dissolved forms:CO2H2CO3HCO-

3CO2-

3

pH is thought to becontrolled bywater/mineral equilibria

Increased T causes pH to increase

Increased P causes pH to decrease

Figure 3: Carbon Dioxide-Bicarbonate-Carbonate Equilibrium


DQB... 2019-2020

Integrated Clausius-Clapeyron Equation

Francisco Diogo Moreira Alves


Integrated Clausius-Clapeyron Equation Slide # 2

ln𝑝𝑝1

∆𝐻𝑅

1𝑇

1𝑇1

The integrated Clausius-Clapeyron equation

figs. 1 and 2 – Rudolf Clausius (on the left) and Émile Clapeyron (on the right). 1

fig. 3 – The phase diagram of H2O. 2

1 Available at: https://mathshistory.st-andrews.ac.uk/ [Accessed 31 May 2020].2 Blundell, S. J., & Blundell, K. M. (2010). Concepts in Thermal Physics (2nd ed.). Oxford University Press Inc., New York.


∆ 𝑉 𝑉 𝑔 𝑉 𝛼 𝑉 𝑔 ≝𝑅𝑇𝑝

d𝐺 𝑉d𝑝 𝑆d𝑇 d𝜇 𝑝, 𝑇 d𝜇𝑔 𝑝, 𝑇

Derivation of the integrated Clausius-Clapeyron equation

𝑉 𝛼 d𝑝 𝑆 𝛼 d𝑇 𝑉 𝑔 d𝑝 𝑆 𝑔 d𝑇

𝑉 𝛼 𝑉 𝑔 d𝑝 𝑆 𝛼 𝑆 𝑔 d𝑇

d𝑝d𝑇

∆𝑆∆𝑉

∆𝐻𝑇∆𝑉

1𝑝d𝑝d𝑇

∆𝐻𝑅𝑇 ⇔

d ln 𝑝d𝑇

∆𝐻𝑅𝑇

ln ∗

ln

d ln 𝑝∆𝐻𝑅

𝑇∗

𝑇

d𝑇1𝑇

∆𝐻𝑅

1𝑇

1𝑇∗ ln

𝑝𝑝∗

∆𝐻𝑅

1𝑇

1𝑇∗

fig. 5 – The chemical potential as a function of temperature. 4fig. 4 – p–T plot of two phases

coexistence line. 3

3 Atkins, P, & de Paula, J. (2010). Physical Chemistry (9th ed.). Oxford University Press.4 Blundell, S. J., & Blundell, K. M. (2010). Concepts in Thermal Physics (2nd ed.). Oxford University Press Inc., New York.


Limitations of the integrated Clausius-Clapeyron equation

fig. 6 – Plot comparison of calculated phase boundary (using the integrated Clausius-Clapeyron equation; p*, T* = ptriple, Ttriple) and a fit of experimental data.

fig. 7 – Enthalpy of vaporization of water dependence with temperature plot. Experimental data from the DDB.

fig. 8 – Plot of the deviation of the values obtained from the integrated Clausius-Clapeyron equation from experimental fit.


Applications of the Clausius-Clapeyron integrated equation

• determining the enthalpy of vaporization and enthalpy of sublimation of a given pure substance, through a linear regression of ln 𝑝 and 1

𝑇.

• determining the neighbouring coexistence curve [of a pure substance], given a specific point 𝑝∗, 𝑇∗ .

• determining the dew point of water, given its measured vapor pressure, in millibars, as ln

.11∆𝐻𝑅

1 1𝑇

,

for quick meteorology calculation.fig. 9 – Dew on a spiderweb, formed as airborne water vapour condenses to form liquid water. By Luc Viatour. 5

5 Available at: https://pt.wikipedia.org/wiki/Ficheiro:Dew_on_spider_web_Luc_Viatour.jpg [Accessed 31 May 2020].


DQB... 2019-2020

Non-Ideal Solid-Liquid Equilibrium

Inês Carolina de Vasconcelos Mendes


Non-Ideal Solid-Liquid Equilibrium Slide # 2

HA I

A BINARY MIXTURE THE IDEIAL AND THE NON-IDEAL

∆𝐻𝑚𝑖𝑠 = 0∆𝑆𝑚𝑖𝑠 = −𝑅 𝑥 𝑙𝑛𝑥 + 𝑥 𝑙𝑛𝑥 ∆𝐻𝑚𝑖𝑠 0


SCHRODER-VAN LAAR EQUATION

https://www.google.com/url?sa=i&url=https://onlinelibrary.wiley.com/doi/10.1002/9783527671403.hlc016&psig=AOvVaw1ufHlQwG_3TiVfm2x9cneu&ust=1591047889737000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCPDWgL2J3-kCFQAAAAAdAAAAABAJ


tetrapentylammonium bromide succinic acid

MOLECULAR BASIS OF NON-IDEALITY

https://www.google.com/url?sa=i&url=https://www.trc-canada.com/product-detail/?T310618&psig=AOvVaw11CxTHw96cTCOE3t8glsZ5&ust=1590949184271000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNCB7d2Z3OkCFQAAAAAdAAAAABAD


E AMPLE


DQB... 2019-2020

Phase Diagram of Pure Compounds

Ana Isabel Fernandes Moreira


Phase Diagram of Pure CompoundsSlide # 2

Phase Diagram

� Phase diagram is a graphical representation that shows the equilibrium conditions between the thermodynamically distinct phases.

� Phase: form of matter that is uniform in terms of chemical composition and physical state.

The phase diagram can be divided into:

• Three distinct regions:

• Three phase separation curves

• Solid Liquid

• Liquid Vapour

• Solid Vapour

Number of phases present

Number of degrees of freedom

Number of components

Number of variables that are not relatedd to the

composition

Gibbs Phases Rule


Phase Transitions

� Phase Transitions: transformation of a substance from one phase to another.

Temperature Pressure


Triple Point and Critical Point

� In the phase diagram, the melting, vaporizing and sublimation curves converge at the triple point.

� Among these three, the vaporization curve is the only one that has a second well-defined point, the so-called critical point, beyond which this curve ceases to exist.

What would happen if the temperature exceeds the critical point?

It would be impossible to condense the gas by increasing the pressure,since the particules have too

much energy for the intermolecular attractions to hold them together as a liquid.

Increases itermolecular forces


Example of phase diagram

The negative slope of the solid-liquid separation line is due to the fact that the molar volume of ice is greater

than that of liquid water. Therefore, the water is denser than the ice.

The pressure increase causes the solid-liquid phase change

Phase diagram of water


DQB... 2019-2020

Energy and Enthalpy of Combustion

Joana Margarida Ribeiro da Silva


Energy and Enthalpy of Combustion Slide # 2

• Combustion is an high-temperature chemical reaction between a fuel and an oxidant, usually atmospheric

oxygen in excess, that produces heat and light.

• When a substance undergoes complete combustion it releases heat as a form of energy.

• In general, the combustion reaction can be represented by the followed equation:

• Since we have the equation, we can determine the standard enthalpy of combustion.

Combustion isan exothermicreaction since

it releasesheat.

nA + mO2 → xCO2 (g) + yH2O (l) + bB + heat of combustion

ΔHc° = -aΔHf°(CO2,g) - yΔHf°(H2O,l) - bΔHf°(B) + nΔHf°(A) + mΔHf°(O2,g)

The heat of combustion can be calculated from thestandard enthalpy of formation (ΔHf°) of the substancesinvolved in the reaction, given as tabulated values.

Standard enthalpy of combustion (ΔHC∘): enthalpy

change when 1 mole of a substance burns (combines vigorously with oxygen) under standard state conditions.

• Heat in a form of energy that in

internal energy is measured at

constant volume and enthalpy is

measured at constant pressure.


• Because it depends on three state functions (U, P, V), it is concluded that

enthalpy is also a state function.

• The change in the enthalpy that occurs during a reaction is equal to the

change in the internal energy of the system plus the product of the pressure

(constant) times the change in the volume of the system:

H = U + PV


• With a bomb calorimeter, it is possible to determine the combustion enthalpyof a certain compound, since this bomb is capable of measuring the heat ofcombustion at a constant volume.

• Since it’s an isochoric process, the heat measured by a bombcalorimeter is equivalent to the change in internal energy:

ΔU =qcal The heat can be determined fromthe temperature change, ΔT, and

the heat capacity of thecalorimeter. qcal=CcalΔT

• Converting from ΔU to ΔH requiresknowing the amount of work done duringthe reaction.

• Being a chemical reaction, work can be easily calculated byreplacing PV and counting the number of moles of gas productsand gas reactants:

ΔH=ΔU+ΔngRT


? Did you know that a substance can burst into flames without the addition of heat from an external source?

• A substance can release heat if it has a relatively low

ignition temperature.

• Spontaneous combustion occurs when there’s a process

that can generate heat (either oxidation in the presence of

moisture and air or bacterial fermentation).

Hay is one of the most studied materials in spontaneous combustion.

• One exemple of this phenomenon would be the haystacks:

Ø Its moisture starts to heat up and the oxygen inside the

hay combines with it and causes a slow burn that

eventually destroys the entire stack.


DQB... 2019-2020

Chemical Equilibrium

Lia Pereira da Costa (up201804835)


Chemical equilibrium

• Chemical/physics aspect:

#19 | Chemical Equilibrium Slide # 2

v₁ v

Example: N2 g 3H2 g ⇌ 2NH3 g

• Thermodynamic aspect:

∂G∂ξ ,

0

μ1𝑛1 μ2𝑛2 ⋯ ⇌ μ3𝑛3 μ4𝑛4 ⋯

In equilibrium:

𝐺1

μ 𝑛 0

G-Função de Gibbsξ-Grau de avanço da reação


Equilibrium constant

Classification of chemical equilibrium in terms of phases

• Homogeneous equilibrium:

HCN aq ⇌ H aq CN aq

• Heterogeneous equilibrium:

CaO (s) + CO2 (g) CaCO3 (s)

𝑎𝐴 𝑏𝐵… ⇌ 𝑐𝐶 𝑑𝐷…For a certain temperature, each reaction of balance has a equilibrium constant that is defined by:

𝐾 ……

ln ∆ 𝐻°

R⇔ ln

∆ 𝐻°

R1 1

Temperature

• Increase the temperature• Decresing the temperature


Factors that affect the chemical equilibrium

Concentration of species involved

• Evolution in the direct direction • Evolution in reverse direction

Le Châtelier principle: "If a chemical equilibrium is subjected to an external change, the equilibrium moves in order to counteract this modification in order to establish a new state of equilibrium."

Pressure

• Increase the pressure• Decresing the pressure

Volume

• Increase the volume• Decresing the volume

Van t Hoff equation


Where you can apply the chemical equilibrium?

CoCl4 2− aq + 6H2O l ⇌ Co H2O 62+ aq + 4Cl− aq

� Variation in the degree of hydration� Temperature variation.


DQB... 2019-2020

ENTHALPY AND ENTROPY OFVAPORIZATION

Luiza H D Fernandes


Enthalpy and entropy ofvaporizationSlide # 2

VAPORIZATION: Refers to changing the state into vapor phase

ENTHALPY OF VAPORIZATION: Amount of enthalpy (heat energy) that is required to transform a liquid

substance into a gas or vapor.

( Hexane molecule / ΔHvap= 28.850 J/mol ) ( Water molecule / ΔHvap = 40,660 J/mol)

DEFINITION

ENTROPHY OF VAPORIZATION: Increase in entropy upon vaporization of a liquid


ENTHALPY OF VAPORIZATION :

ΔHvap = ΔUvap + P ΔV ΔUvap = Variation of internal energy of the vapor phase

P = Pressure

ΔV = Volume Variation

- Enthalpy x First Law of Thermodynamics ΔU = Q+ W

ENTHROPHY X ENTHALPY

ENTROPHY OF VAPORIZATION

ΔSvap = ΔHvapTvap

ΔSvap = Entrophy of Vaporization

ΔHvap= Enthalphy of Vaporization

Tvap = Boiling Point


GIBBS FREE ENERGY

- Gibbs Free energy (ΔG) was created in order to predict the spontaneity of a chemical reaction

ΔG = ΔH – TΔS

ΔG = Gibbs Free Energy ΔH= Enthalphy VariationT = Absolut Temperature ΔS= Entrophy Variation

H2O (l) -> H2O (g)

ΔH 0 ΔS 0

AG <0 Spontaneous Process

AG = 0 Dynamic Balance

AG> 0 Non-spontaneous Process

ΔH ΔS ΔG Reaction

ΔH < 0 ΔS 0 - Spontaneous

ΔH > 0 ΔS<0 + Non-spontaneous

ΔH < 0 ΔS<0 ?Spontaneous: T<0

Non-

Spontaneous:T>0

ΔH > 0 ΔS 0 ? Spontaneos: T>0

Non-Spontaneous:

T<0


CURIOSITIES

Trouton's rule: For many (but not all) liquids,

the entropy of vaporization is approximately

the same at ~85 J mol−1K−1.

High Enthalphy of Vaporization x Life on Earth


DQB... 2019-2020

Equation of state of an ideal gas

Student Name: Cristiana Filipa Costa Oliveira


Equation of state of an ideal gas Slide # 2

Definitions • Equation of state

• State functions

• T (temperature, K) • P (pressure, Pascal) • n (amount of substance, mol) • V (volume, m3)

• Ideal gas Law • PV=nRT

• R (gas Constant)

• Real gas vs Ideal gas

Chang, R., & Goldsby, K. (2013). Química. AMGH Editora Ltda.


• Boyle law

• Pressure – volume ratio • isothermal transformation

𝐏 ∝𝟏𝐕

𝐏 𝐊𝟏𝟏𝐕

𝐏𝐕 𝐊𝟏

𝐏𝟏 ∙ 𝐕𝟏 𝐏𝟐 ∙ 𝐕𝟐 ⇐ when T constant



• Charles and Gay – Lussac Law

• temperature-volume ratio • isobaric and Isochoric transformation

V∝ 𝐓 V 𝐊𝟐 𝐓 𝑽𝟏

𝑻𝟏

𝑽𝟐

𝑻𝟐

P∝ 𝐓 𝐏 𝐊𝟑 𝐓 𝑷𝟏

𝑻𝟏

𝑷𝟐

𝑻𝟐

• Avogadro Law • volume-quantity ratio

V∝ 𝐧 V 𝐊𝟒 𝐧 𝐏𝐕 𝐊𝟒


Equation of state of an ideal gas Slide # 5 Chang, R., & Goldsby, K. (2013). Química. AMGH Editora Ltda.

• Equation of state an ideal gas

• 𝐵𝑜𝑦𝑙𝑒 𝐿𝑎𝑤 ∶ 𝑉 ∝𝑃

(n, T constant) • 𝐶ℎ𝑎𝑟𝑙𝑒𝑠 𝐿𝑎𝑤 ∶ 𝑉 ∝ 𝑇 (n, P constant) • 𝐴𝑣𝑜𝑔𝑎𝑑𝑟𝑜 𝐿𝑎𝑤 ∶ 𝑉 ∝ 𝑛 (P, T constant)

• 𝑉 ∝ 𝑇𝑃

; 𝑉 𝑅 𝑇𝑃

𝑜𝑢 𝑷𝑽 𝒏𝑹𝑻

• when conditions vary: • 𝑃 𝑉

𝑇𝑃 𝑉

𝑇

• Equation of van der waals

• 𝑃 𝑑𝑒𝑎 𝑃 𝑒𝑎𝑎𝑉

• 𝑉𝑒 𝑒 𝑒 𝑉 𝑛𝑏

• 𝑷 𝒂𝒏𝟐

𝑽𝟐 𝑽 𝒏𝒃 𝒏𝑹𝑻

corrected pressure

corrected volume


DQB... 2019-2020

IONIZATION EQUILIBRIUM OF A MONOPROTIC ACID

Juliana Esteves Martins


Ionization Equilibrium of a Monoprotic AcidSlide # 2

A monoprotic acid is an acid that donates only one proton per molecule to an aqueous solution.

Ionization is a process of ion formation when an acid is dissolved in water.

Ionization equilibrium of a monoprotic acid is given by

𝐻𝐴 𝑎 ⇌ 𝐻 𝑎 𝐴 𝑎

𝐾𝐴 𝐻𝐻𝐴

𝐾 log𝐾 e 𝐻 log 𝐻

Equação de Henderson-Hasselbalch

𝐻 𝐾 log𝐴𝐻𝐴

𝐾

𝐾 ∝ 𝑖The higher the 𝐾 , the more ionized the acid,

then the greater it´s strength

𝐻 𝐾 ⇒ 𝐻𝐴 𝐴𝐻 𝐾 ⇒ 𝐻𝐴 𝐴𝐻 𝐾 ⇒ 𝐻𝐴 𝐴

Only applies to weak acidsBuffer range: 𝐾 1 𝐻 𝐾 1

CHANG, Raymond; GOLDSBY, Kenneth A. Química 11 ed. AMGH Editora Ltda, 2013https://pt.wikipedia.org/wiki/Equação_de_Henderson-Hasselbalch

https://pt.wikipedia.org/wiki/Equa%C3%83%C2%A7%C3%83%C2%A3o_de_Henderson-Hasselbalch


When we study the ionization equilibrium of a monoprotic acid we can do its titration simultaneously with potentiometric and conductimetric measurements, for example.

pH combinedeletrode

Condutimetriccell

pH measurements

Conductivity measurements

we get the pH and conductivity curves and the first and second derivates of tritation

𝑘 𝑘𝑉 𝑉

𝑉

used to correct the effect of dilution on the conductivity curve

V_base V_base

https://moodle.up.pt/pluginfile.php/3653/course/section/26731/TP%2305_DEMO_RESULTS.xlsx?time=1589101032496

https://moodle.up.pt/pluginfile.php/3653/course/section/26731/TP%2305_DEMO_RESULTS.xlsx?time=1589101032496


Depends on

pH of solution and theconductivity in each point

Concentration of the species involved

Monoprotic acid volume and concentration andtitrant concentration

Conductivity

The concentration of all ions in solution

The variables are all interconnected

pH of solutionAdded titrant volume

Equivalent volume


ApplicationAn application of this theme is the ionization equilibrium of acetic acid and is a case similar to the ionization equilibrium of glycylglycine (diprotic acid) that we studied.

CuriosityDid you know that ionization equilibrium can be compared to ventilation of thehuman organism? Vs

What information can we extract?

𝑘 𝑖

The combination of the two curves allows us to

determine the values of the ionic molar conductivity of

the ions in solution.

𝑃90% HA and 10% 𝐴

𝑃100% 𝐴

𝐾50% HA and

50% 𝐴

𝐾50% HA and

50% 𝐴

𝑃99% 𝐴 and

1% HA

https://moodle.up.pt/pluginfile.php/3653/course/section/26731/paper_Chemical%20edutation_Glycil%20glina.pdfhttps://moodle.up.pt/pluginfile.php/3653/course/section/26731/LBS_pH_Simulator_V04.xlsx

https://moodle.up.pt/pluginfile.php/3653/course/section/26731/paper_Chemical%20edutation_Glycil%20glina.pdf

https://moodle.up.pt/pluginfile.php/3653/course/section/26731/LBS_pH_Simulator_V04.xlsx


DQB... 2019-2020

Temperature Dependence of the Ionic Conductivity

Mariana Arantes Azevedo


Temperature Dependence of the Ionic Conductivity 1

Introduction

Objective: Understand the physicochemical factors that condition thesolution conductivity and its temperature variation.

Factors

Ionic conductivity is the electrical conductivity due to the motion of ionic charge.

Ionic radius

Pressure

Ionic concentration

Viscosity of solvent

Fig1. Temperature dependence of ionic conductivity

molar conductivity of the ion (S.cm2 mol-1z ionic charge of the ion being consideredF Faraday constant

mobility of the ion


• Conductivity variation with ionic radius

Conductivity increases with the increase of the ionic radius to the cesium, then begins to decrease

• Conductivity variation with pressure

For smaller ions, there is an increase in ionic conductivitywith pressure, but this conductivity begins to decrease whenpressure becomes high.For larger ions, such as cesium, conductivity decreases pressure due to the effect of levitation.

Fig 2. Variation of experimental values of limiting ionic conductivity as a funcion of experimentally derived ionic radim, for monocovalent cations in H2O at 298 K.

Fig. 3. Pressure dependence of experimental ionic conductivity of (a) Li+, (b) K+, (c) Cs+ and (d) tetramethylammonium (TMA+) ion in water at 298 K.


Slide 3

Temperature Dependence of the Ionic Conductivity Slide 4

Fig 4. Variation of (a) experimental ionic conductivity as function of ionic radius at different temperatures, (b) activation energy, Ea as a function of ionic radius and (c) pre-exponential factor, A as a function

of ionic radius, ri for cations in H2O.

• Variation of conductivity with solvent viscosity

According to Walden's rule, ion conductivity decreaseswith increased viscosity of the solvent

Variation of conductivity with ion concentration

The more concentrated a solution is, the higher the conductivity is. In most cases it is a proportional relationship. *ExceptionSome solutions have a limit to how conductive it can be. Once that pointis reached, increasing the solution concentration will actually lower

conductivity. This is observed in sulfuric acid solutions.

Fig 5. Conductivity in function of solvent viscosity

Fig 6. Concentration in function of ionic conductivity of NaClTemperature Dependence of the Ionic Conductivity Slide 5

Arrhenius and Vogel-Fulcher-Tammann equations

These equations describe the variation of ionic conductivity with temperature in various types of solutions (aqueous, organic liquids, polymers, ionic liquids).

Arrhenius equation Vogel-Fulcher-Tammann equation

k reaction constantA A he i constant (pre-exponential factor)Ea activation energyR U i e al gas constant ( 8,31 J/mol/K)T absolute temperature

T ideal gla a i i e e a e (temperature at which viscous flow starts)Tg e e a e a hich he i c i reaches a certain high value 1013 P (glass-transition temperature)D i e el i al he f agili f the liquid

Temperature Dependence of the Ionic Conductivity Slide 6


DQB... 2019-2020

André Filipe Sousa Rodrigues


EXTENDED DEBYE-HÜCKEL EQUATION

Extended Debey-Hückel Equation Slide # 2

Peter Debye Erich Hückel

• Solutions containing ionic solutes do not perform optimally, even at very low concentrations.

• Objective of the Debye-Hückel theory: to estimate the activity coefficients, γ.

• This factor considers the interaction energy of the ions in solution.

All equations were taken from the book Physical Chemistry of Ira Levine

Debye-Hückel equation

representation of the ion distribution in a solution


Deduction of the equation

All equations were taken from the book Physical Chemistry of Ira Levine

• - ( molality-scale) ionic strength of the solution

• z - ion charge from which the activity coefficient is being calculated

• A and B - constants whose values depend on the dielectric constant and temperature

• a - effective ion diameter in solution (the unit is Amstrong)

Debye-Hückel equation: (used withhigher ionic strength)

Debye-Hückel limiting law: (used with lowerionic strength and very dilute solutions)

Extended Debey-Hückel Equation Slide # 4All equations were taken from the book Physical Chemistry of Ira Levine

Extended Debye-Hückel equation

Using the SI values

• , , , • 78,38• 997,05 Kg/m3

(for H2O at C and 1 atm)

𝐴 1,1744 (Kg/mol)1/2

𝐵 3,285 10 (Kg/mol)1/2 m-1

• To eliminate the empirically determined ionic diameter• we note that, for 3 Å• 0.328 /Å 1

Eletrolyte activitiy coefficients at higherconcentrations proposed by Davies


Equation applications

Plots of log10 g versus square root of ionic strength for some aqueous electrolytes at 25°C and 1 atm. The dotted lines show the predictions of the Debye Hückel limiting law (10.65).

The graphic was taken from the book Physical Chemistry of Ira Levine

• Study of chemical processes• Calculation of z+z-• Compare values of experimental

loads and values of literature

• Limiting law equation begins to deviate from real values for larger ionic strength

• Oppositely charged ions have some tendency to associate with ionic pairs in solution.

• For the same ionic strength, the theory gives better results for values of z+|z-| smaller (e.g. works better for 1:1 electrolytes than for 2:2)

LABQFLABORATORY OF PHYSICAL CHEMISTRY

DQB... 201 -2020

Temperature Dependence of the Heat Capacity

Filipa Leça Santos

PHYSCHEM a _To ic#25

Temperature Dependence of the Heat Capacity Slide # 2

Heat Capacity

• Heat capacity is the amount of hea required for raising e e a e of an object by unit temperature.

• At constant pressure, dQ dU pdV

• At constant volume, dV 0, dQ dU

Where:C : Heat capacity [J/K]c : Specific heat [J/(kg・K)]m : Mass [kg]Δ𝑄: Internal energy [J]ΔT: Temperature [K]

C C mc

Isobaric process

Isochoric process

Temperature Dependence of the Heat Capacity Slide # 3

A constant-volume bomb calorimeter. An example ofthe application of the concept heat capacity, where inthis case it is heat capacity at constant volume, C

dU C dT dH CpdT

Cv and Cp

U T at constant volume H T at constant pressure

H vs T U vs TCp C

Temperature Dependence of the Heat Capacity Slide #

Variation of heat capacity

1º order 2º order

3 3K T 3K

Temperature Dependence of the Heat Capacity Slide #

Curiosities

Nega i e e e a eNega i e hea ca aci

Wa e high hea ca aciEa h c i a e

Ec eLife


DQB... 2019-2020

Mariana Lopes Damas Carvalho


SOLID-SOLID TRANSITION

Solid-Solid Transition Slide # 2

Solid-Solid Transition

1st order transitions

2nd order transitions

Volume ,V Enthalpy,H Chemical Potential ,µ Entropy, S Heat Capacity,Cp


Transition exemples 1st order transitions

2nd order transitions

Grafite (s) Æ Diamante (s)

paramagnetic ferromagnetic


Techniques

DTA -Differencial thermal analysis DSC -Differential Scanning Calorimetry TGA- Thermogravimetric Analysis

DTA Thermal Curve


Curiosity Tin pest

white tin gray tin


DQB... 2019-2020

Dynamic Equilibrium of a Chemical Reaction

André Sousa Santos

PHYSCHEMlab_ Dynamic Equilibrium of a Chemical Reaction

Dynamic Equilibrium of a Chemical Reaction Slide # 2

Dynamic equilibrium

https://descomplica.com.br/artigo/o-que-e-equilibrio-quimico/4Qb/

Rate of the reaction


Le Chatelier’s PrincipleVariation Equilibrium shift

Increase of the products concentration Q>K left

Decrease of the products concentration Q<K right

Increase of the reactants concentration Q<K right

Decrease of the reactants concentration Q>K left

https://moodle.up.pt/pluginfile.php/104280/mod_resource/content/4/14__EQUILIBRIO_2020.pdf


Relationship Between Equilibrium and Rate Constants

Consider the reaction:A⇌B

where A denotes the reactants and B denotes the products. The equilibrium constant, Keq, is defined as:

Keq=[B]eq/[A]eq

where [A]eq represents the reactants at equilibrium conditions and [B]eq represents the products at equilibrium conditions.

The rate of the reaction is given by:

d[A]/dt=−kf[A]+kb[B]

where kf is the rate constant for the forward reaction and kb is the rate constant for the backward reaction. The equilibrium constant can also be calculated by dividing the rate constant of the forward reaction by the rate constant of the reverse reaction:

Keq=kf/kb

where A and B are in equilibrium.

https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Chemical_Equilibria/Principles_of_Chemical_Equilibria/Dynamic_equilibrium

Dynamic Equilibrium of a Chemical ReactionSlide # 5

Harrison and Buckly (2000)

• Indigo Carmine• Sodium Hidroxyde• Glucose

https://www.ejmste.com/download/dynamic-equilibrium-explained-using-the-computer-4028.pdf


DQB... 2019-2020

Conductivity Measurements of Electrolyte Solutions

Catarina Esteves da Silva Batista Ferreira


Conductivity Measurements of Electrolyte Solutions Slide # 2

CONDUCTIVITY

Definitions

Units

Measurements

Aplications

https://andyjconnelly.wordpress.com/2017/07/14/conductivity-of-a-solution

https://andyjconnelly.wordpress.com/2017/07/14/conductivity-of-a-solution

Conductivity Measurements of Electrolyte Solutions Slide # 3

What parameters influence an electrolyte conductivity?

• Concentration-as the ion charge in solution facilitates the conductance of the electric current, the conductivity of a solution is highly (but not entirely) proportional to its ion concentration.

• Temperature- it is extremely important to work with constant temperatures. To compensate for temperature changes, conductivity readings are usually corrected to the value at a referencetemperature, typically 25 ° C

• Substance-Strong electrolyte ( HCl)-: are substances that are fully ionised in solution.

Weak electrolyte (CH3COOH) -: are substances that are not fully ionised in solution. For example, acetic acid partially dissociates into acetate ions and hydrogenions, so that an acetic solution contains both molecules and ions.

https://www.colby.edu/chemistry/CH141/CH141L/CH141Lab4Fall2009.pdf

https://www.colby.edu/chemistry/CH141/CH141L/CH141Lab4Fall2009.pdf

IConductivity Measurements of Electrolyte Solutions Slide # 4

What affects the measurements ?

http://www.analytical-chemistry.uoc.gr/files/items/6/618/agwgimometria_2.pdf

• Applying an alternating current: the measuring current will flow through the double layercapacitance (Cdl) of the electrodes

• Optimising the electrode areas: increasing the active surface area of the electrodes with a layer of platinum black reduces the current density and consequently the polarisationeffect.

• The cell constant value is an important factor of conductivity measurements. The calibration of thesystem is normally done with a known substance, KCL, although the latest devices are alreadyinstalled automatically.

• Position of conductivity cell:make sure that all the poles of the conductivity cell are completelycovered by the sample. Always position a 2-pole cell in the center of the measuring vessel.

http://www.analytical-chemistry.uoc.gr/files/items/6/618/agwgimometria_2.pdf

IConductivity Measurements of Electrolyte Solutions Slide # 5

Curiosities:

Large amounts of salts(NaCl)- Textil IndustrylMeasuring the conductivity of very diluteelectrolyte solutions, drop by drop

https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_Chem1_(Lower)/08%3A_Solutions/8.10%3A_Ions_and_Electrolytes/8.10.9C%3A_8.10.9C%3A__Weak_and_Strong_Electrolytes

These curves can be explained by the fact that a strong electrode hascomplete dissociation, while a weak electrode has a balance, it depends onthe concentration / temperature of the two species.

Use of large amounts of sodium chloride (electrolytefunction - the ions transport the dye from the solution to the fiber), thus increasing the conductivity of the dyewastewater.

https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%253A_Chem1_(Lower)/08%253A_Solutions/8.10%253A_Ions_and_Electrolytes/8.10.9C%253A_8.10.9C%253A__Weak_and_Strong_Electrolytes


DQB... 2019-2020

ISOMERIZATION EFFECT IN THE VAPORIZATION OF ALCOHOLS

Beatriz Rocha


Isomerization Effect in the Vaporization of Alcohols Slide # 2

Endothermic process; ∆vapG°= ∆vapH° -Tref ∆vapS°

Clausius-Clapeyron: ln 𝑝 𝚫 𝑝 ° × + 𝐶Same molecular formulaDifferent structure → different physical properties

Isomerism for Alcohols Vaporization


The stronger the intermolecular forces that are holding a liquid together, the more energy that will

be required to pull them apart (higher temperature)

VaporizationHeat of vaporization• INTERMOLECULAR FORCES

Temperature

Number of moles of liquid phase

Vapor pressure of gas phase

Entropy• TRANSLATIONAL AND ROTATIONAL MOTION OF

MOLECULES

∆vapH° (kJ/mol)

n - Butanol 52

sec - Butanol 48

iso – Butanol 51

tert - Butanol 46

NIST• Trouton’s rule


∆vapH° (kJ/mol) ∆vapS° (J/(mol.K)) ∆vapG° (kJ/mol) Tboil (K)

propanol C3H8O 45,938 124,97 5,0075 370,3

iso –propanol C3H8O 44,884 127,35 3,2593 355,5

butanol C4H10O 50,694 129,25 7,6073 390,6

iso - butanol C4H10O 49,831 134,46 5,7940 380,8

Case Study

Relative Volability

∆G° = -RT ln (peq)

Tboil confirms

Linear vs Ramified Alcohols

Ramified (iso-) ↑ volatile

∆vapG° (↑ volability)

↑ ∆vapS° (↑ liquid phase organization)

Carbon Chain Size

Bigger chains – volability

↑ ∆vapH°Æ predominant effect

https://sites.google.com/site/alcoholsvolatility/home

↑ ∆vapS° (↑ liquid phase organization)

NIST

∆vapG°Æ↑ volatile


Industry Research

Azad, A., Rasul, M. (2019) Advanced Biofuels: Applications, Technologies and Environmental Sustainability

« to incorporate the benefits of butanol isomers for commercial purposes, there is a need to conduct a wide range of engine studies

with various parameters »

Mack et al. (2016) Experimental investigation of butanol isomer combustion in Homogeneous Charge Compression Ignition (HCCI) engines

n-butanol and isobutanol – biofuels ↑ Energy content ∆vapH° (butanol) improves the cold start behavior of

an engine

Cripwell, J. et al. (2018) SAFT-VR Mie: Application to PhaseEquilibria of Alcohols in Mixtures with n-Alkanes and Water

“Hydrogen bonds …have a tendency to dictate thethermodynamics behaviour of these componentes”

Kacar, G., Width, G. (2016) Hydrogen bonding in DPD: application to low molecular weight alcohol – water mixtures

"hydrogen bonding is implemented in DPD (Dissipative ParticleDynamics) to measure liquid properties"

LABQF2020LABORATORYOFPHYSICALCHEMISTRY

DQB...2019-2020

Equilibrium Phase Transition

INÊSDEALMEIDAMARQUES

PHYSCHEMlab_EquilibriumPhase Transition#01

Equilibrium Phase Transition Slide#2

Conditionforaphaseequilibrium:!" = !$

!equalsGmPure substances

!" = !$

∆' =∆(

)


Liquid- Vapor and Solid-Vapor Equilibrium

∆*+ = *+, -./

− *+, /12341

≈ *+, -./

6* = 78) ∆*+ ≈8)

6

46

4)=6∆(+

8)2

42:6

4)=∆(+

8)242:6

4(1))≈−∆(+

8

ln>?>@≈

A∆BC

D(@

E?−

@

E@)

Solid-Liquid Equilibrium

F 46 = F∆GH/'

∆GH/*4) = F

∆GH/(

)∆GH/*4)

?

@

?

@

?

@

62 − 61 ≈∆GH/(

∆GH/*2:)2)1

Solid-Solid Equilibrium


which factors influence phase equilibrium?

∆(

∆'

which molecular factors influence ∆(I∆'?

Molecularsize

Morespecialinteractions,likehydrogenbonds

Degreeofdisorder


DQB... 2019-2020

Inter and Intra Molecular Interactions

José Mesquita


Inter and Intra Molecular Interactions Slide # 2

There are, essentially, two different kinds of interaction: intramolecular andintermolecular. Intramolecular interaction refers to the force that binds the atomswithin a molecule together, while the intermolecular interaction is what keeps themolecules connected like a thread, with these being a lot weaker thanintramolecular ones.

Different interactions result in specific variations of certainproperties and this idea will be presented later in thispresentation.

References: Khan Academy and Chemistry LibreTexts

https://www.khanacademy.org/science/class-11-chemistry-india/xfbb6cb8fc2bd00c8:in-in-states-of-matter/xfbb6cb8fc2bd00c8:in-in-intermolecular-forces/a/intramolecular-and-intermolecular-forces

https://chem.libretexts.org/


Types of molecular interactions, by descedingorder of strength:• Hydrogen bonding• Dipole-dipole bonding

London formula





Stronger forces:

Boiling pointsMelting points

Enthalpy of fusionEnthalpy of vaporization

Viscosity

Entropy of fusionEntropy of vaporization





Drug design





DQB... 2019-2020

Critical point and supercritical fluid

ANA ISABEL DA COSTA CAMPINHO


Critical point and supercritical fluid Slide # 2

Critical point and supercritical fluid


Phase diagram and properties

Density(Kg/m³)

Viscosity(µPa s)

Gases 1 10

Supercriticalfluids

100-1000 50-100

Liquids 1000 500-1000


Solvent Molecular mass(g/mol)

Criticaltemperature (K)

Critical pressure(MPa)(atm)

Critical density(g/cm³)

Methanol(CH3OH)

32,04 512,6 8,09 (79,8) 0,272

Ethanol(C2H5OH)

46,07 513,9 6,14 (60,6) 0,276

Pr = !!" Tr = ##"

Vr = $$"

Corresponding states law

Vr – Reduced volume Vc – Critical volumePr – Reduced pressure Pc – Critical pressureTr – Reduced temperature Tc – Critical temperature


Application and curiosities


DQB

Edi e Fe ei a Pin o

PHYSCHEM a _Topic#33

S ecia ion in he Ioni a ion E ilib i m of a Di o ic Acid

S ecia ion in he Ioni a ion E ilib i m of a Di o ic Acid Slide

H A aq ⇌ H aq HA aq 𝐾 HA aq ⇌ H aq A aq 𝐾

• A di o ic acid i a ecific e of ol o ic acid ha can lo e o o on

• Pol o ic acid di la a man e i alence oin in i a ion c e a he n mbe of acidic o on he ha e

• A di o ic acid i mboli ed b H A

𝑝𝐻 log H 𝐾

H HAH A 𝐾

H AHA

In od cion

Figure 01 D Fo m la and molec la fo m la of o alic acid Figure 02 D Fo m la and molec la fo m la of ch omic acid


Specia ion g aphic and i a ion c e

Speciation: efe o he di ib ion of an elemen among chemical ecie in a em Th i ba ed on he a m ion ha all com onen and de i ed ecie a e in e ilib i m and i he de c i ion of he ab ndance of ecie of an elemen in a ol me ecie di ib ion o ab ndance

Figure 03 – Ti a ion c e of di o ic acidi h a ong ba e NaOH

a Ca bonic acidb Maleic acidc O alic acid

Figure 04– S ecia ion diag am of Ca bon S ecie

Main factors affecting speciation• Tem e a e T• 𝐾 values• pH;• P e ion p


Figure 05 Il a ion of he acid ba e o en iome

Figure 06 Il a ion of he acid ba e i la ion.

Specia ion mea emen and e al a ion echni e

Figure 07 Il a ion of heca illa elec o ho e i em

Figure 0 Il a ion of he ch oma og a hic me hod


Applica ion

Figure 13 D Fo m la and molec la fo m la of ca bonic acid

Sol bili

Ne o an mi eamino acid

Figure 0 Molec la fo m la of gl c lgl cine

Figure 10 Ne o an mi e

Figure 12 Ne o emFigure 11 Dige i e em

Figure 14 Il a ion of ea a e


DQB... 2019-2020

Concentration Dependence of the Ionic Conductivity

Inês Maria Manso Santos


Concentration Dependence of the Ionic Conductivity Slide # 2

What is Ionic Conductivity?

• Movement of ionic charge in response to na electric field.

Fig. 3. NaCl solution conductivity as a function of NaCl concentration. The solid line is drawn to guide the eye. The data were obtained from the literature. A.H. Galama, N.A. Hoog, D.R. Yntema Method for determiningion exchange membrane resistance for electrodialysissystems

Electrolyte- substance that produces na electrically conducting solution whem dissolvedin a polar solvent.They can be a strong or weak eletrolyte.

Eletron flow

Charge

Anode CathodeEletrolyte

https://www.sciencedirect.com/topics/materials-science/conductivity


Electrolytic cell

Conductivity Molar conductivity

Units: S 𝑚 Units: S 𝑚 𝑚𝑜𝑙

The diferences between Conductivity and Molar Conductivity

Molar

Con

ductivity

Con

ductivity

Concentration Concentration


Strong eletrolyte:• Complete ions dissociation

Wealk eletrolyte:• Parcial ions

dissociation

Some of the Electrolyte Functions:

• Mantain plasma osmotic pressure

• Maintenance of physiological pH

• Regulate heart and muscle function

• Participates in redox reactions


Examples and Conclusion:

Concentration increases Ionic movementincresases

Decrease of molar conductivity

Concentration increases Decrease of ionsdissociation

Decrease of molar conductivity


DQB... 2019-2020

Triple point in a phase diagram

Ricardo Moreira


Triple point in a phase diagram Slide # 2

Phase Diagram

Figure 1-Phase Diagram of water

• Type of chart used to show conditions (pressure, temperature, volume, etc.) at which thermodynamically distinct phases occur and coexist at equilibrium.

• Examples of phase diagrams include:• 2-dimensional diagrams, the simplest of which are pressure-temperature diagrams of pure substances, like water;• Binary phase diagram;• and, crystals or polymorphs, like the phase diagram of ice phases.

Figure 2- Phase diagram of water where the roman numerals represent ice phases.


Triple point

• Point in which any 3 phases are in equilibrium• Point at which two or more curves meet• For e ample the triple point of merc r occ rs at a temperat re of °C and a pressure of 0.2 mPa• The term "triple point" was coined in 1873 by James Thomson, brother of Lord Kelvin


Application

• The triple point of water was used to define the kelvin, the base unit of thermodynamic temperature in the International System of Units (SI).

• The value of the triple point of water was fixed by definition, rather than measured, but that changed with the 2019 redefinition of SI base units.

• The triple points of several substances are used to define points in the ITS-90 international temperature scale, ranging from the triple point of hydrogen (13.8033 K) to the triple point of water (273.16 K or 0.01 °C).


Curiosity (Helium-4 and CO2)• In addition to the triple point for solid, liquid, and gas phases, a triple point may involve more than one solid phase, for substances with multiple

polymorphs. Helium-4 is a special case that presents a triple point involving two different fluid phases (lambda point).

Figure 4-Phase diagram of CO2Figure 3-Phase diagram of Helium-4

http://faculty.chem.queensu.ca/people/faculty/mombourquette/Chem221/5_PhaseChanges/PhaseDiagrams.asp


DQB... 2019-2020

GAS PHASE HEAT CAPACITY

Ana Teresa Gonçalves e Silva


Gas Phase Heat Capacity Slide # 2

Heat Capacity (J.K-1)

amount of heat to be supplied to a given quantity of a compound to produce a unitchange in temperature

• Isochoric CV

• Isobaric Cp 𝐶 ° 𝐴 𝐵 𝐶 𝐷 (Shomate Equation)

References: Wikipedia and Levine, Ira N.; “Physical Chemistry”, pp.53-55

𝐶𝑑𝑞𝑑𝑇

Ideal gas 𝐶 , 𝐶 , 𝑅

Figure 1 – Graphical representation of enthalpy and internal energy infunction of temperature and derivations of each plot.


Degrees of freedomnumber of independente coordinates needed to specify a molecule’s position and configuration

3N (molecule with N atoms)

• Translational degrees of freedom

• Rotational degrees of freedom

• Vibrational degreees of freedom9 3N-5 linear molecules9 3N-6 nonlinear molecules

Figure 2 – Representation of the spacing between energy levels for the differentenergy componentes.

References: Garland, Carl W.; Nibler, Joseph W.; Shoemaker, David P.; “Experiments in Physical Chemistry”, pp.10 -118

𝐶 𝐶 𝑎𝑛 𝐶 𝑜 𝐶 𝑖𝑏 𝐶 𝑒𝑙 𝐶 𝑖𝑛 𝑒


Diatomic ou polyatomic molecules E E trans E rot E vib

References: Garland, Carl W.; Nibler, Joseph W.; Shoemaker, David P.; “Experiments in Physical Chemistry”, pp.10 -118

HEAT CAPACITY RATIO FOR AN IDEAL GAS

≡ ,

,1

,

• Adiabatic Expansion Method• Sound Velocity Method

Figure 3 – Graphical representation of molar heatcapacity of mercury in function of temperature.

Figure 4 – Heat capacity of diatomic gases.

Monoatomic ideal gas 𝐶 , R

Gas Phase Heat Capacity Slide # 5References: http://casey.brown.edu/chemistry/misspelled-researh/crp/Edu/Documents/00_Chem201/4_third_law/4-third_law-frames.htm

Applications

Entropy

S∆𝐶𝑇 𝑑𝑇

Industry

9 Exchanges of energy in reactors9 Thermoelectric power generation

Figure 5 – Determination of entropy from heat capacity data.


DQB... 2019-2020

Undercooled Liquids

INÊS FILIPA CABRAL REAL LIBÂNIO


Undercooled LiquidsSlide # 2

What are Undercooled Liquids?

“Supercooling/undercooling is the process of chilling a liquid below its freezing point, without it becoming solid”.

(https://www.sciencedaily.com/terms/supercooling.htm)

Figure 1 - ”By supercooling liquids, scientistscan determine the physics happening inglasses”.by Pacific Northwest National Laboratory

https://phys.org/news/2012-06-supercooling-liquids-scientists-physics-glasses.html

Examples of undercooling :

→ Refrigeration;

→ Animals use the phenomenon of supercooling

that allow them to remain unfrozen and avoid

cell damage and death;

→ Many plant species located in northern climates

can acclimate under these cold conditions by

supercooling. Figure 2 - Gibbs energy diagram, evidence thatthe supercooled liquid has a higher G (therefore itis more unstable) than the solid for T <Tm.

https://www.sciencedaily.com/terms/supercooling.htm

Undercooled Liquids Slide # 3

The process of undercooling

Many materials undergosupercooling. Supercooling is relatedto the material’s nucleation andsolidification mechanisms. Thedegree of its supercooling isinfluenced by:

1. The sample size2. Homogeneity3. Cooling rate4. Sample container surface morphology

Another technique that can be useis scratching.

A glass is formed by cooling a liquid fastenough to avoid crystallization. Atcontinued supercooling the liquidviscosity increases dramatically, and atsome point the liquid freezescontinuously into a noncrystalline solid.

http://www.mendelset.com/articles/680/preparation-recrystallization-acetanilide

https://phys.org/news/2012-06-supercooling-liquids-scientists-physics-glasses.html

Figure 4 - ”Bysupercooling liquids,scientists candetermine the physicshappening inglasses”.by Pacific NorthwestNational Laboratory

Figure 3 – Scratchingtechnique.


On what does it depend & Why?

file:///C:/Users/inesr/Downloads/Robin_cornell_0058O_10327.pdf

Figure 5 - “Phase diagram of water.Water at a pressure of 1 bar issupercooled when its temperatureis lower than the correspondingfreezing temperature: 0°C “.

Physically, supercooling exists becausethe nucleation of the ice phase requiresto overcome an energy barrier. Thisenergy barrier decreases withincreasing supercooling.

The difference in Gibbs free energy betweenthe supercooled liquids and crystalline phase(ΔG) is given by Gibbs equation:

Δ" # = Δ% # − #Δ' #

The enthalpy change can be estimated by:

Δ% #= Δ%()* + ,

-.

-Δ/01# , Δ' # = Δ'()* + ,

-.

- Δ/03 1#

The viscosity of a liquid approaching theglass transition always becomesextremely large.

4 = ŋν71


Application Example

Example: Undercooled water (http://www1.lsbu.ac.uk/water/supercooled_water.html)

Figure 6 - Supercooled water diagram.http://www1.lsbu.ac.uk/water/supercooled_water.html

- ”Liquid water, cooled below its melting point, is

thermodynamically less stable than ice but

typically remains liquid (in a metastable state) for

a few degrees below 0°C and then forms solid

hexagonal ice if shaken or after seemingly

random periods of time”.

Figure 7 – ”Volume difference (Δν)between supercooled water and solidice”.

http://www1.lsbu.ac.uk/water/supercooled_water.html http://www1.lsbu.ac.uk/water/supercooled_water.html

Figure 8 – “Water activity of supercooledwater in equilibrium with ice IH”.

- ”At 228.15 K the density of supercooled

water equals that of hexagonal ice”.

- ”A model for the thermodynamic properties

of supercooled water has been developed that

gives its heat capacity, vapor pressure, density,

thermal expansion and water activity”.


DQB... 2019-2020

TEMPERATURE DEPENDENCE OF CHEMICAL EQUILIBRIUM

Joana Patrícia Teixeira


Temperature Dependence of Chemical Equilibrium Slide # 2

Chemical Equilibirum

Factors that influence the chemical equilibrium:9 Concentrations of the species involved;9 Volume;9 Pressure;9 Temperature.

∆𝐺 ∆𝐻 T∆𝑆High temperature

∆𝐺 negative

Low temperature

∆𝐺 positive


The form of the temperature dependence can be taken from the definition of the Gibbs function ( al e of G i dependen on empera re):

∆𝐺T

∆𝐺T ∆𝐻

1T

1T

∆𝐺 RTlnK

⇔ lnKK

∆HR

1T

1T

Van't Hoff equation

⇔RT lnKT

RT lnKT ∆𝐻

1T

1T

⇔d lnKd T

∆𝐻RT

∆𝐻 i inde endenof em e a e


N g Oendothermic

exothermic2NO g

Endothermic Reaction: Heat absorption.

Exothermic Reaction: Releases heat.

How does temperature influence chemical equilibrium?

Favors direct reaction(formation of products)

Equilibrium shiftsto the right

Favors reverse reaction(formation of reagents)

Equilibrium shiftsto the left

disfavor the entropic state

favors the entropic state


Equilibrium Constant (𝐊𝐜

Temperature Temperature

The temperature change alsoaffects the equilibrium constantof the system (K )

More NO will be formed, increasing the concentration

K value increases

If N and O increasing the concentration

K value decreases

𝐾𝑝𝑟𝑜𝑑 𝑐𝑡𝑠𝑟𝑒𝑎𝑔𝑒𝑛𝑡𝑠 K=1

K<1K>1

∆𝐺 = 0∆𝐺 is positive∆𝐺 is negative

Increasing the temperature Increasing the temperature

ExothermicEndothermic

K increase decrease

K descrease increase


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Glass Transition Phenomenon

José Miguel Silva FerrazUp201805115


Glass Transition Phenomenon Slide # 2

Glass Transition Phenomenon

Not considered a phase transition

Amorphous Solid Rubbery SolidT

Brittle Glassy State Viscous Rubbery State

The glass transition of a liquid to a solid-like state may occur with either cooling or compression.

Smooth increase in the viscosity

By supercooling

Physical Chemistry 6th Edition Levine/ Physical Chemistry Atkins&Paula 8th Edition

The term phase transition is used to describe transitions between different states of matter.

Ehrenfest Classification

Second Order Phase TransitionDynamic Phenomenon VS

On what does this phenomenon dependand what information can we get from it?


Transition temperature Tg

The glass transition temperature, Tg, is atthe point of intersection of extrapolations

of the two linear parts of the curve.

The glass transition and elastic models of glass-forming liquids - Jeppe C. Dyre / Encyclopedia of Materials Science and Technology

• Constant Cooling rate• Viscosity Threshold of 1012 Pa.s• History of the material (its processing)• Molecular Weight• Composition

If the liquid is a good glass former

Measurement of Tg (the temperature at the point A) by differential scanning

calorimetry (DSC)

Glass Transition Phenomenon Slide # 4Netzsch Glass Transition Temperature /The glass transition and elastic models of glass-forming liquids - Jeppe C. Dyre

Why do we need it?

Describes the temperature region wherethe mechanical properties of the

materials change from hard to brittle to more soft, deformable or rubbery

Drug delivery

Food conservation

Glass Ceramics

Fiber Glass

Polymer Science

Sorbitol


Ka mann Pa ado

The entropy of ethylbenzene obtained by extrapolation

Kau mann s Temperature

Supercooled Liquid

Lower Entropy Than

Crystal Phase

Paradox!!

Is there a possible solution??

The temperature where the extrapolated liquid entropy meets the crystal entropy.

By extrapolating the entropy of the supercooled liquid below its glass transition

temperature.Tha s Impossible!!

Kau mann s paradox and the glass transition Robin J.Speedy / The glass transition and elastic models of glass-forming liquids - Jeppe C. Dyre


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Phase Separation in Binary Mixtures

Ana Margarida Gomes Moreira Alves


Phase Separation in Binary Mixtures Slide # 2

F = 3 → 3 intensive variables: T, p and molar fraction

Amount of matter that is- physically distinguishable;- chemically uniform;- can be separated from a mixture.

Theoretical concepts

PHASE SEPARATION

Creation of two distinct phases from a single homogeneous mixture

PHASE

The Gibbs Phase Rule

F = C – P + 2

C = 2 and F = 4 – PApplied to a binary mixture:

On what does it depend & Why?

Miscibility


The composition of the two phases in the equilibrium varies with the temperature!

Liquid-liquid phase diagram

Mixture composition

Temperature of the system

Considering a temperature-composition diagram (p constant):

Atkins Physical Chemistry, Eight Edition; @2006 Peter Atkins and Julio de Paula


T

χ

LCST

Critical solution temperatures

Liquid-liquid phase diagram

UCST

T

χ

Upper critical solution temperature, TUCSTLower critical solution temperature, TLCST

Water and triethylamine Hexane and nitrobenzene


Completly miscible

Partially miscible

NICOTINE AND WATER: Closed miscibility loop

Atkins Physical Chemistry, Eight Edition; @2006 Peter Atkins and Julio de Paula

Nicotine forms complexes

Affect the miscibility of the compounds

Number of fases at a certain temperature is affected

Curiosity: Nicotine can be extracted from tobaccodust and after further treatment has beneficial effects on Parkinson s disease

Liquid-liquid phase equilibria in nicotine (aqueous) solutions; Nikola D.Grozdanic, et al.


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Phase Rule

BÁRBARA NEIVA SAMPAIO

PHYSCHEMlab_Phaserule#41

Phase Rule Slide # 2

It is a rule that can make the connection between all the variables in a system in thermodynamic equilibrium. All phase diagrams can be discussed by this rule.This concept is based on the fact that if two phases are in thermodynamic equilibrium, their chemical potentials will be the same.

Temperature

Pressure

Molar fraction

Fig 1. A metal alloy

Fig2. The Gibbs phase rule

Some examples of intensive variables


For a 1 component system:

Fig3. Phase diagrams

1 Phase

2 phases

3 phases

Line in the phase diagram

Triple point

F=C-P+2

No negative values of F


For a 2-component system:

Inside the line: F= 3-2=1Outside the line: F= 3-1 = 2 Fig 5. Temperature-composition diagram

Fig4. Vapor-pressure diagrams


Fig 6. The lever rule

Fig8. Temperature-composition diagram of a azeotopic composition mixture

Fig 7. Differential scanning calorimetry

Fig 9. Liquid liquid phase diagram


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TEMPERATURE DEPENDENCE OF PHYSICAL PROCESSES

Fátima Daniela Aguiar Gonçalves


#42 | Temperature Dependence of Physical Processes Slide # 2

Temperature is a measure of the average kinetic energy of the particles in a system. Adding heat to a system causes its temperature to rise.

There is a minimum temperature, known as absolute zero, at which all molecular motion stops.

Matter can exist in a solid, liquid or gaseous state. Under the condition of constant pressure, temperature is the primary determinant of a

substance's phase.

Figure 1. Comparison of temperature scales

Tem

pera

ture

HeatDiagram 1. Phase changes with temperature Figure 2. Particle model of states of matter

Temperature T and States of Matter


Heat Capacity

!" =$δ& "

= δ'δ& "

d' = $ + * ⟺ d' = $ − -./

! J 1 K34 = $∆&

Heat capacity is defined as the ratio of the amount of energy transferred to a material and the change in temperature that is produced.

It is dependent on temperature itself, as well as on the pressure and the volume of the system and their changes.

Constant volume

!6 =$δ& 6

= δ7δ& 6

7 = ' + -/

Constant pressure


Temperature Dependence of Solubility

Solubility is the ability of a solute to dissolve in a solvent and form a solution.The solubility of a given solute in a given solvent typically depends on temperature.

Solid SolubilityThe dissolution of many salts is endothermic.The increase of the kinetic energy destabilizes the solid state, allowing the solvent to

more effectively break the intermolecular attractions in the solute.

Application in Recrystallization

Diagram 2. Solubility diagram of some salts

Purification by Recrystallization

Figure 5. Purification of benzoic acid by recrystallization

#42 | Temperature Dependence of Physical ProcessesSlide # 5

Gas Solubility• In Polar Solvents

In solvents like water, the dissolution of most gases is exothermic (ΔH<0).

solute(gas) ⇌ solute(aq) + Δ

• In Non-Polar SolventsWeaker solvent-solvent and the solvation enthalpies.In many cases, the enthalpy needed to break solvent-solvent interactions is comparable to

the enthalpy released in making solvent-gas interactions (ΔH≈0).

Δ + solute(gas) ⇌ solute(sol)

Temperature Dependence of Solubility

Diagram 3. Solubility diagram of some gases in water (polar solvent)

∆# = ∆% − '∆( < 0 if spontaneous

∆%+,- = ∆%+,-./01+,-./0 + ∆%+,-./01+,-304/ + ∆%+,-304/1+,-304/∆%+,-./01+,-./0 567 = 0


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Solutions of weak electrolytes.

Mariana Silva Almeida


Solutions of weak electrolytes Slide # 2

What is a solution?

Basic conceptsSolution: It’s a mixture of two of more substances(solute(s) and solvent). It exists in different phases.Electrolyte: Means loosened electricity because separatingthese ions through dissolution frees them to actindepedently and carry their electrical charge around.

Solute

Solvent

What is an electrolyte?

Solution

Fig 2: Solution process.

Fig 3: The role of electrolytes in the body.Fig 1: Solvation of the sodium cation.


Weak Electrolytes

Weak Electrolytes: organic acids, some inorganic acids, some inorganic bases low conductivity in solution.

Weak ElectrolytesWeak acids Weak bases

Hydrofluoric acid, HF Ammonia, NH3

Acetic acid, CH3COOH Pyridine, C5H5N

Carbonic acid, H2CO3

Phosporic acid, H3PO4

Table 1: Examples of weak electrolytes.

Examples of dissociation equations for a weak acid and a weak base, respectively:

CH COOH H O ⇋ H+ CH COO

C H N H O ⇋ C H NH+ OH

Electrolytes

StrongElectrolytes

Strongacids

Strongbases

WeakElectrolytes

Weak acids

Weak bases


A study on conductivity

Fig 4: Water by itself does not conduct electricity. Fig 5: Adding salt or any other ionic solid in the water, it will dissolve into the respective component electrolytes

Fig 6: Electrolytes are responsible for conducting electricity.

Nonelectrolyte solution Strong electrolyte solution weak electrolyte solution

Fig 8:Different solution conductivities.

Fig 7: Conductivity measures.

Solutions of weak electrolytes. Slide # 5

⋀Kc S m mol ,

where c is the molar concentration of the solution.

Molar conductivity:

Fig 10: Molar conductivity vs concentration of the

electrolyte.

Electrolytes and ConductivityConductivity:

κ G K S mwhere G is the condutance and K

the cell constant

Strongelectrolyte

Weakelectrolyte

κKCL κ

Cond

uctiv

ity

Cond

uctiv

ity

Fig 9: Conductivity vs concentration of the electrolyte.

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