Download Lectures 1-6 - TCD Chemistry

School of Chemistry Course 1101
Introduction to Physical Chemistry
Professor J.M. Kelly)
(Lectures 1-6)
LEARNING OBJECTIVES
Intermolecular Forces, Solids, Liquids, and Solutions
After these lectures you should:
(a)
Know about the main types of intermolecular forces.
{London (dispersion), dipole-dipole, ion-dipole, hydrogen-bonding)
(b)
Know about the main features of the solid state structures (unit cells,
coordination numbers, packing fractions etc.)
For elements, cubic – and hexagonal- close packing; body-centred and facecentred cubic structures:
For ionic compounds NaCl and CsCl structures. Octahedral and tetrahedral holes.
Examples of network and molecular solids
(c)
Know about the Born-Haber cycle: calculation of lattice energy/enthalpy (ΔHL)
(d)
Understand the principal features of the phase diagrams of pure compounds
including pressure dependence of melting and boiling points, triple point and
critical point, variation of vapour pressure with temperature.
(e)
Be familiar with ΔH and ΔS of phase transitions.
(f)
Know about the factors affecting solubility of liquids; ideal solutions, entropy
of mixing; real solutions, effect of intermolecular forces on ΔH of solution.
(g)
Know about the effect of pressure and temperature on the solubility of gases in
liquids. Henry’s law. Application of Le Chatelier’s principle.
(h)
Understand thermodynamics cycles to explain qualitatively ΔH and ΔS of
solution for ideal non-ionic and ionic solids. ΔH of hydration of ions. Effect of
temperature on solubility and its relationship to ΔH of solution (ΔHsoln )
Some useful equations
At melting point ΔHfus = TΔHfus + ΔHmix
For dissolution of non-ionic compounds
ΔHsoln = ΔHfus + ΔHmix
For dissolution of ionic compounds
ΔHsoln = - ΔHL + ΔHH
{Note lattice energy (enthalpy) ΔHL is negative
Hydration enthalpy ΔHH is negative}