12-1 CHEM 102, Spring 2013 LA TECH Instructor: Dr. Upali Siriwardane e-mail: [email protected]...

12-1CHEM 102, Spring 2013 LA TECH

Instructor: Dr. Upali Siriwardane

e-mail: [email protected]

Office: CTH 311

Phone 257-4941

Office Hours: M,W 8:00-9:00 & 11:00-12:00 am;

Tu,Th,F 9:30 - 11:30 am.

Test Dates:

Chemistry 102(01) Spring 2013

September 27, 2013 (Test 1): Chapter 12 & 13

April 24, 2013 (Test 2): Chapter 14 & 15

May13, 2013 (Test 3) Chapter 16 & 17

May 15, 2012 (Make-up test) comprehensive: Chapters 12-17 9:30-10:45:15 AM, CTH 328


REQUIRED :

Textbook: Principles of Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro - Pearson Prentice

Hall and also purchase the Mastering Chemistry

Group Homework, Slides and Exam review guides and sample exam questions are available online:

http://moodle.latech.edu/ and follow the course information links.

OPTIONAL :

Study Guide: Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro 2nd Edition

Student Solutions Manual: Chemistry: A Molecular Approach, 2nd Edition-Nivaldo J. Tro 2nd

Text Book & Resources

http://moodle.latech.edu/


Chapter 12. Solutions

12.1 Thirsty Solutions:

12.2 Types of Solutions and Solubility

12.3 Energetics of Solution Formation

12.4 Solubility Equilibrium and Factors Affecting solution Formation

12.5 Expressing Solution Concentration

12.6 Colligative Properties: Vapor Pressure, Freezing Point, Boiling Point, Osmatic Pressure

12.7 Colligative properties of Strong Electrolytes


Solution Terminology

soluteone or more substance(s) dispersed in the solutionsolventmajority substance in a solutionThe solubility of a solid in a solvent is typically given in

g/100 ml.

Types of solutionsMixture of GasesLiquid solutions (L+S,L+L,L+G)Solid solutions (S+S, alloys)Aerosols (L+G)Foam (S+G)


Miscible vs. Immiscible


“Likes Dissolve Likes”

Materials with similar polarity are soluble in each other. Dissimilar ones are not.

Polar substances with similar forces are likely to be soluble in each other

Non-polar solutes dissolve in non-polar solvents

stronger solute-solvent attractions favor solubility, stronger solute-solute or solvent-solvent attractions reduce solubility


Solubility of Ionic Compounds and Temperature


Solution Terminology

Miscible - liquids that dissolve in each otherImmiscible - liquids that do not dissolve in each

other due to differences types of interactionsSaturated solutionA solution that contains as much it can hold Unsaturated solutionA solution that contains less than maximum

amountSupersaturated solution A solution that contains more than maximum

amount


Types of Solutions (Diluted, Saturated, and Supersaturated)


Supersaturated Solution


Solute - Solvent Interactions


The Solution Making Exopthermic Process


The Solution Making Endothermic Process


Thermodynamic Factors Affecting Solubility

1. Energy: Enthalpy (DH) Lower energy – DH

2. Order: Entropy (DS) Disorder + DS

Exothermic –DH favors solubility: product favored

Mixing (+DS disorder favors solubility: product favored

Gibbs Free Energy: (Chapter 18)

DGsoln = DHsoln -TDSsoln,


Types of Solute - Solvent Interactions

All interactions are electrostatic force

~ Coulombic: proprotional to charge and separation)

1. London Dispersion Forces: (O2 dissolved in Liq. N2)

2. Ion-Ion Interaction: (Ionic liquids in batteries)

3. Ion-Dipole Interaction (hydrated ions Na+

(aq))

4. Dipole-Dipole Interaction (CCl4 in benzene (C6H6)

5. Hydrogen Bonding. (water and éthanol)


1) What are the main factors affecting a solubility of a solute in a solvent?


The Solution Making Exopthermic Process


The Solution Making Endothermic Process


2) Arrange the following inter-particles forces in liquids and solids in the order of increasing strength:

ion-ion,

ion-dipole,

hydrogen bond,

dipole-dipole and

London dispersion


3) Identify the most important type of inter-particle force for each of the following compounds:

a) NaCl(s) or NaCl(l) b) N2(l) or N2(s)

c) N2(g) d) Na(s) and Na(l)

e) H2O(l) or H2O(s) f) CH3CH2OH(l) or CH3CH2OH(s)


4) Which of the above inter-particle force could be named as intermolecular force?

a) NaCl(s) or NaCl(l) b) N2(l) or N2(s)

c) N2(g) d) Na(s) and Na(l)

e) H2O(l) or H2O(s) f) CH3CH2OH(l) or CH3CH2OH(s)


Acetic acid

HC2H3O2

CH3COOH

Hexanol

C6H13OHHexane

C6H14

Propanoic acid

C2H5COOH

“Like Dissolves Like”

Identify Hydrogen Bonding, Polar and Non-polar groups in Covalent Molecules


5) What types of inter-particle forces

solute-solute:DH1,

solvent-solvent: DH2,

solvent-solute:DH3) are involved when

a) CH3CH2OH(l): dissolved in water,H2O:

DH1 = ; DH2 = ; DH3=

For covalent compounds: DHsoln= DH1+ DH2+ DH3


Water Dissolving An Ionic Solute


Solution Process of Ionic Compounds


Hydration of a Sodium Ion


Heats of Solution


5) b) Na2SO4(s) dissolved in water:

DH1 = ; DH2 = ; DH3 =

Ion-ion inter-particle forces in solids are called Lattice Energy. ( this is related to DH1)

Ion-water inter-particle forces are called Hydration Energy (this is related to DH2 and DH3)

For ionic compounds; DHsoln = DHlattice + DHhyd

Qualitatively speaking which of the above a) or b) would have a more exothermic DHsoln?


6) Assign the entropy (most +, medium + or least +) for i) S1 –solute:

ii) S2-solvent:

iii) S3, solution (solvent-solute):

For the following: (Indicate which one is highest, intermediate and lowest order) For

a) CH3CH2OH(l): dissolved in water:

S1 = ; S2 = ;S3=

Na2SO4(s) dissolved in water:

S1 = ; S2 = ;S3 =


5) Qualitatively speaking which of the above a) or b) would have a more positive DSsoln?

a) CH3CH2OH(l): dissolved in water:

S1 = ; S2 = ;S3=

b) For Na2SO4(s) dissolved in water:

S1 = ; S2 = ;S3 =


7) Why sand is insoluble in both polar and nonpolar solvents?


8) How does temperature and pressure affect the solubility of following?

a) NH4NO3(solid) in water with +(positive) DHsoln:

b) CO2 gas in water:


Solubility of Oxygen in Water


Henry’s Law


Henry’s LawSolubility of Gases in SolventsSg = kHPg

where

Sg solubility

kH Henry’s Law constant

Pg partial pressure of gas

Increasing the pressure of a gas above a liquid increases its solubility


9) Deep sea divers may experience a condition called the "bends" if they do not readjust slowly to the lower pressure at the surface. Using the diagram on pressure dependence solubility of gases on water explain this phenomenon.


Solution Concentration Units a) Molarity (M)

b) Molality (m)

c) Mole fraction (Ca)

d) Mass percent (% weight)

e) Volume percent (% volume)

f) "Proof"

g) ppm and ppb


Molarity

The number of moles of solute per liter of solution.

molarity M

moles of soluteM =

liter of solution

units molar = moles/liter = M


An aqueous solution 58.5 g of NaCl and 2206g water has a density of 1.108 g/cm3. Calculate the Molarity of the solution.

58.5 g 1 mole Solution volume 58.5 g + 2206 g in L

1.00 mole NaCl Molarity of NaCl solution = ------------------------- = 0.489

M 2.044 L solution

2264.5 g solution 1 cm3 solution 1 L solution= 2.044 L solution

1.108 g solution 1000 cm3 solution

Molarity Calculation


Molalitynumber of moles of solute particles (ions or

molecules) per kilogram of solvent#moles solute

m = #kilograms of solvent

Calculate the molality of C2H5OH in water solution which is prepared by mixing 75.0 mL of C2H5OH and 125 g of H2O at 20oC. The density of C2H5OH is 0.789 g/mL.


125 g of H2O = 0.125 kg H2O

1.284 mole C2H5OH

Molality(m) = ------------------------ = 10.27 m

0.125 kg H2O

75.0 mL C2H5OH 0.789 g C2H5OH 1 mole C2H5OH= 1.284 C2H5OH

1 mL 46.08 g C2H5OH

Molarity Calculation


Mole Fraction#moles of component i

Xi = total number of moles

Calculate the mole fraction of benzene in a benzene(C6H6)-chloroform(CHCl3) solution which contains 60 g of benzene and 30 g of chloroform.M.W. = 78.12 (C6H6) M.W. = 119.37 (CHCl3)


moles of a na

Mola Fraction(ca) = ------------------- = --------------

moles of na + moles nb na + nb

a = C6H6

b = CHCl3

nC6H6

Mola Fraction(ca) = ------------------

nC6H6 + nCHCl3

m.w (C6H6) = 78.12 g/mole m.w (CHCl3) = 119.37 g/mole 60/78.12 = 0.768 mole C6H6 30/119.37 = 0.251 mole CHCl3

ca(C6H6) = 0.768/ 0.786+ 0.251 =0.754

Ca(CHCl3) = 0.0.251/ 0.786+ 0.251 = 0.246 1.000

Mole Fraction Calculation


Weight Percent #g of solute

wt % = 102

#g of solution

Volume Percent

#L of solute

Vol % = 102

#L of solution

Proof

proof = Vol % x 2


Problem

What is the mole fraction of ethanol, C2H5OH, in ethanol solution that is 40.%(w/w) ethanol, C2H5OH, by mass?

a. 0.40 b. 0.46 c. 0.21 d. 0.54


Parts per Million

#g of solute #mg of solute

ppm = 106 =

#g of solution #kg of solution

#mL solute ppm =

#L of solution

Parts per Billion

#g of solute #micro-g of solute

ppb = 109

=

#g of solution #kg of solution


ppm and ppb conversions1 ppm = (1g/ 1x 106g) 1x 106

= (1/1000 g) x 1x 106

1x 106 / 1000g

= mg/ 1x 103 g

= mg/ L

1 ppb = (1g/ 1x 109g) 1x 109

= (1/1000000 g)

1x 109/1000000g

= mg/ 1x 103 g

= mg/ L


A solution of hydrogen peroxide is 30.0% H2O2 by mass and has a density of

1.11 g/cm3

. The MOLARITY of the solution is:

a) 7.94 M b) 8.82 M c) 9.79 M d) 0.980

e) none of these

M.W. = 34.02 (H2O2)

Problem


10) Define following solution concentration units:

a) Molarity (M) b) Molality (m)

c) Mole fraction (Ca) weight)

d) Mass percent (%

e) Volume percent (% volume)

f) "Proof"

g) ppm and ppb


Comparison of Concentration Terms


11) Compare the advantages and disadvantages of these solution concentration parameters.


12) Determine the number of moles of solute present in 416 mL of 3.75 M HBr solution.(Atomic weights: Br = 79.9, H = 1.008).


13) Determine the mass (g) of solute required to form 25 mL of a 0.1881 M H2O2 solution. (Atomic weight - O = 16.00, H = 1.008).


14) A concentrated solution of AgNO3 is 21.9% by weight and the density is 1.220 g/cm3. How many grams of the solution are required to prepare 150.0 mL of a 0.200M solution?(Atomic weights: Ag = 107.87, N = 14.01, O = 16.00).


15) A solution of carbon tetrachloride, CCl4, in benzene (C6H6) is 0.010 m. What mass (g) of CCl4 is in 50.0 g of benzene?(Atomic weights: C = 12.01, H = 1.008, Cl = 35.45).

12-1 CHEM 102, Spring 2013 LA TECH Instructor: Dr. Upali Siriwardane e-mail: [email protected]...

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Transcript of 12-1 CHEM 102, Spring 2013 LA TECH Instructor: Dr. Upali Siriwardane e-mail: [email protected]...