Entropy

Topic 13

What is lattice energy

Energy change when one mole of a solid ionic compound is formed from its gaseous ions

what factors can affect lattice energy

ion charge, ion size

what is standard enthalpy change of atomisation

energy change when one mole of gaseous atoms is formed from its elements

what is first electron affinity

energy change when each atom in one mole of atoms gains one electron to form a 1- ion

why is the first electron affinity of group 8 positive

Repulsion between electrons, new electron is going in a new shell

why are second electron affinities typically positive

Two negative species repelling each other

how can we calculate experimental lattice energy

born haber cycle

how can theoretical lattice energy be found

x-ray crystallography

what assumptions should be made when calculalting lattice enthalpy

ions are in contact, ions are spherical, charge is evenly distributed

what is covalency caused by

polarising of anion by cation

What is polarising power

Ability of an ion to attract electrons towards itself

what types of ions are more easily polarised

high charge + small cation, high charge + large anion

what is enthalpy change of solution

enthalpy change when one mole of an ionic solid dissolves in water to form an infinitely dilute solution

what is enthalpy change of hydration

enthalpy change when one moles of an ion in its gaseous state is completely hydrated by water

what is a spontaneous process

one that takes place without continuous intervention from us

how can you best describe entropy

quantity associated with randomness and disorder

what is total entropy change

sum of entropy change of the system and entropy change of surroundings

what does total entropy need to be in order to be spontaneous

positive

how do you calculate Delta S system

products - reactants

how is Delta S Surroundings calculated

negative Delta H / T

for an exothermic reaction where delta H is negative what will Delta Surroundings be so what happens to entropy

DS surroundings will be positive, so entropy of surroundings increases

will DS surroundings be positive or negative for an endothermic reaction

negative