Notes for Part 1 (IMF Reprise and Gases)

Chemistry IA: Energy & Equilibrium – Part 1;

CHEMISTRY IA

2015 Scott Theatre

Mon (10 am)

Tue (11 am)

Wed (9 am)

LECTURER & COURSE COORDINATOR

Prof Greg Metha

(lecturer)

Badger Laboratory,

Room 105a

[email protected]

Lecture questions

Email is the most efficient way to contact us!

Dr Natalie Williamson

(coordinator)

Badger Laboratory,

Room 223

natalie.williamson@

adelaide.edu.au

Course and Lab related issues

Prescribed Text:

"Chemistry" 2nd edition

Blackman, Bottle,

Schmid, Mocerino, Wille

Available from UniBooks

This slide is not

shown in lectures

• No workshops this week, start in week 2

• The questions are designed to assist your

learning. Do them!

• Attempt the workshop questions before going.

• There is a Help Desk – check the O-week lecture

notes to find out more.

WEEKLY WORKSHOPS This slide is not

shown in lectures

mailto:[email protected]






• During Semester 1, a total of 4 computer

assignments must be completed and they are worth

20% of your final assessment.

• Assignment 1 is due in week 4

Friday 27th March

• See MyUni (or the Course handbook) for other

Tutorial dates

COMPUTER ASSIGNMENTS This slide is not

shown in lectures

• No laboratory practicals this week BUT

• You have Computer Practical Exercise that you

should complete.

• Remember to complete the Computer Practical

Exercise before you commence the Laboratory

Practical.

PRACTICALS This slide is not

shown in lectures

• Two non-compulsory in-semester lecture tests

• 1st test – Week 7, 2nd test – Week 12

• They potentially make up 20% of your grade

• Lecture test marks will be redeemable in the end of

semester exam

MCQ LECTURE TESTS This slide is not

shown in lectures

A better world with Chemistry


Designing Pharmaceuticals

Can we use the molecular

properties of molecules to

indicate their usefulness as

drugs?

Selectivity and efficacy

Breakdown products

(are they toxic?)

This slide is

not examinable Supra-Molecular Chemistry

Nanoscale reaction vessels:

• non-standard conditions

• altering reaction outcomes

• accelerate/select reactions to occur

• stabilise reactive intermediates

Drug Delivery

• water soluble

Separation and Sensing

This slide is

not examinable

Clean Energy: Photo-catalytic

Generation of H2 from Water

Potentially a clean, cheap

source of energy

Need to develop better

catalysts

H2 can run cars and tractors!

New Holland NH2 tractor

This slide is

not examinable What Can We Do With CO2?

CO2 is a very stable molecule

(thermodynamic sink)

Can bury it!

Or use it as a chemical feedstock

Mitsui Chemicals announced in

Sept 2008 that it will build a pilot

plant to generate MeOH from CO2

(for olefin production)

This slide is

not examinable


SEMESTER 1:

Energy & Equilibrium (8 lectures)

Atoms to Molecules (8 lectures)

Main Group Chemistry (8 lectures)

Transition Metal Chemistry (8 lectures)

THIS YEAR'S CHEMISTRY TOPICS

SEMESTER 2:

Acids, Bases & Electrochemistry (12 lectures)

Structure Determination (6 lectures)

Synthetic & Bio-organic Chemistry (18 lectures)

OUR TOPICS

1. Gases (§ 6)

2. Chemical Thermodynamics (§ 8)

3. Chemical Equilibrium (§ 9)

4. Solubility (§ 10)

"Chemistry": Complete reading list available on MyUni

ENERGY&

EQUILIBRIUM

Enthalpy, Heat

(1st & 2nd Laws)

Entropy, Free Energy

(3rd Law)

Reaction

Rates

Acids & Bases

pH, pKa

Chemical

Equilibrium

Titrations

Buffers

Reaction

Energetics

Electrochemistry

Inter-

Molecular

Forces

Gas

Laws

Solids &

Liquids

Molecular

Geometry

ACIDS, BASES &

KINETICS

YEAR 11 & 12

MO THEORY BONDING

INTRAMOLECULAR

strong

hold atoms together

bonding electrons

INTERMOLECULAR

weak attractions

between molecules

give bulk properties


Ionic bonds are strong but they can be readily

disrupted in aqueous solution due to the formation

of …..,

Ion – Ion Bonding

Electrostatic attraction between cations and

anions e.g. NaCl

Naughty atoms

Consider Na+/K+ in the body:

Na+ O

H -

+

+

Ion - Dipole Forces

Electrostatic attraction between ions and

polar molecules

Dipole - Dipole Forces

Electrostatic attraction between polar molecules

E.g. HCl H2CO

Cl

H -

+

Cl

H -

+

C

H

-

+

H O

C

H

-

+

H O

Dipole - Dipole Forces

+

+

_

_

+

+

_

_

H

O

H

H

O

H

Called hydrogen-bonding when H atom is

directly bonded to N, O or F atoms

E.g. NH3, H2O and HF

C:/Users/a1002827/Uni/Teaching/Lectures/Level 1/Chem1/2013/extra_slides_v6.pptx#1. PowerPoint Presentation


Induced Dipoles

A non-polar molecule like N2 has no

permanent dipole

However, the electron "cloud" can be

distorted to create an induced dipole

(Think of electron density moving

about within an atomic orbital)

N N

. . - +

- + . .

Induced Dipoles

Interaction with an ion or dipole distorts the

electron cloud of the non-polar molecule

Transient - lasts as long as the interaction

ION - INDUCED DIPOLE and

DIPOLE - INDUCED DIPOLE

. .

. . + . .

- +

+

- +

Induced Dipole – Induced Dipole

Interactions between

non-polar molecules

Collisions with

neighbours induces an

instantaneous dipole

which gives rise to an

attraction b/w molecules

These weak attractive forces are often called DISPERSION FORCES or "LONDON FORCES"

Polarisability

The magnitude of the

induced-dipole depends

on the ease of distortion

This polarisabilty is related to

no. of electrons in the molecule

E.g. Difference in Tb

for halogens

E.g. Difference in Tm for alkanes

(CH4 vs C20H42)


States of Matter: Solids

• Small distance between atoms/molecules

• Small ‘free’ volume

• Strong intermolecular forces cf RT energy

• Very ordered structure

• Little movement of atoms/molecules

RT – thermal energy available at Room Temperature

(25 ºC 298.15 K)

This equates to an average ~10 kJ/mol of energy (Chem II)

States of Matter : Liquids

• Small distances between atoms/molecules

• Small ‘free’ volume

• Moderate intermolecular forces cf RT energy

• Short range order

• Some movement of atoms/molecules

States of Matter : Gases

• Long distances between atoms/molecules

• Large ‘free’ volume

• Weak intermolecular forces cf RT energy

• Complete disorder

• Random movement of atoms/molecules

Matter & Energy

There is a relationship between

the states of matter and energy

SOLID LIQUID GAS

MELTING

SUBLIMATION

BOILING

H2O movie

C:/Users/a1002827/Uni/Teaching/Lectures/Chem1/Accessories/Water.mpg


Solid, Liquid or Gas?

Increasing intermolecular forces increases:

melting point & boiling point

energy of melting & energy of vapourisation

We will be investigating energy changes

associated with phase transitions

2 Important Molecules

H2O boiling point = 373 K @ 1atm.

CO2 sublimes at 195 K @ 1 atm.

Difference due to strength of IMF

.. .. O O C

H

O

HBut states can vary with

Pressure & Temperature

At T = 273.16 K (0.01 °C)

P = 611.73 Pa (0.006 atm.)

H2O exists as a

solid, liquid and gas

Triple Point of H2O

Phase diagram for H2O

At T = 217 K (–56.6 °C) and P = 5.1 atm,

CO2 exists as a

solid, liquid and gas

Exists as dry ice at

T < 194.7 K (–78.5 °C)

@ 1 atm.

Triple Point of CO2

Phase diagram for CO2


Geo-sequestering CO2

This slide is

not examinable

The proposal to capture CO2,

compress it and pump it into

reservoirs within the Earth is

known as "geosequestration". The

CO2 is compressed to the point

where it is a supercritical fluid (see

critical point on phase diagram).

There is concern that some of the

CO2 will dissolve or react to form

other substances.

It is currently being trialed in

southern Victoria.

"Chemistry" 1st Edition, Chapter 6 page 209

GASES (Chapter 6)

Molecular model:

Atoms & Molecules

- immediately fill available space

- constant & random motion

- frequent ‘elastic’ collisions

Under ‘normal’ conditions governed by

well-defined laws involving P, V & T

Pressure

Pressure is the force operating on a unit

area

force

P =

area

SI UNITS: Pascal (Pa)

1 Pa = 1 kg / m x s2

1 atm = 101,325 Pa

Boyle’s Law

Pressure is related to

Volume

Robert Boyle

(1627-1691)

British scientist


Boyle’s Law

1

P

V

or

PV = constant

Charles’s Law

V T

or

V = constant x T

Jacques Charles

(1746-1823)

French physicist

& chemist

Some Ballooning History

After realising that hydrogen was

lighter than air, Charles made the

first balloon using H2 gas and on

August 27 1783 the balloon

ascended to a height of 914

meters.

Upon landing outside of Paris, it

was destroyed by terrified

peasants.

Charles was elected to the French

Académie des Sciences in 1785

www.centennialofflight.gov/essay/Dictionary/Charles/DI16.htm

This slide is

not examinable

Absolute T

Extrapolate to zero V

T = 273.15 ºC

Plot V vs T for

different gases


P T

or

P = constant x T

Kinetic Energy & Gases

Increasing T - increases kinetic energy of gas

I) Constant P, Volume increases

II) Constant V, Pressure increases

http://accad.osu.edu/~midori/GasLaw.html

Visual demonstration: Effect of T and V on Pressure

Avogadro’s Law

Equal volumes of different gases

(at the same T & P) contained the

same number of molecules.

Related to this was Avogadro's realisation that

molecular gases were composed of atoms bound

together. The idea of atoms and molecule was not

generally accepted until after his death.

Amedeo Avogadro

(1776-1856)

Italian chemist

volume occupied by gas

Molar volume =

number of moles of gas

Avogadro’s Law

At T = 0 C and P = 1 atm, 1 mole of gas has a

constant molar volume: 22.41 dm3

273.15 K

1 mole = 6.022 x 1023 molecules = NA

http://accad.osu.edu/~midori/GasLaw.html


Must know:

PV = nRT

P: pressure (in Pa)

V: volume (in m3)

n: no. of moles

R: gas constant = 8.314 J K1 mol1

T: temperature (in K)

Ideal Gas Law

J kg m2 s–2

R can have other units; 0.08206 L atm K–1 mol–1

Gas Mixtures

Many gases are mixtures of 2 or more gases

(A, B etc.). The atmosphere is N2, O2, CO2, H2O ….

According to the model of Ideal Gases, only the

total number of moles is important:

P V = ntotal R T

ntotal = nA + nB + …..

Ptotal = PA + PB + …..

This is Dalton's Law of Partial Pressures Exp 3

Gas Mixtures

Warning: many gas mixtures do not follow

this ideal behaviour because the have

different IMF or because they react! Exp 3

Mole Fraction of Gas Mixtures

Chemical composition of gases can be described

quantitatively by n or P. Can also use fractions:

Mole fraction (moles per total mole)

Mole fraction of A = XA = nA ∕ ntotal = PA ∕ Ptotal

Moles per million moles – parts per million

(or parts per billion)

This is not the same when ppm is defined in

terms of mass! (i.e. 10 ppm of Hg in soil)

Notes for Part 1 (IMF Reprise and Gases)

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Transcript of Notes for Part 1 (IMF Reprise and Gases)