Thermodynamics

Question 1

enthalpy of lattice dissociation

Answer 1

standard enthalpy change when 1 mole of a solid ionic compound is broken up into its free gaseous ions

Question 2

enthalpy of lattice formation

Answer 2

standard enthalpy change when 1 mole of solid ionic compound is formed from its gaseous ions

Question 3

enthalpy of formation

Answer 3

enthalpy change when 1 mole of a substance is produced from its constituent elements under standard conditions, with reactants and products in their standard states

Question 4

ionisation energy

Answer 4

enthalpy change to remove 1 mole of electrons from 1 mole of gaseous atoms for form 1 mole of gaseous 1+ ions

Question 5

enthalpy of atomisation

Answer 5

The enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state

Question 6

bond enthalpy

Answer 6

mean of enthalpy change when 1 mole of covalent bonds is broken, with all species in the gaseous state, average over a range of different compounds

Question 7

electron affinity

Answer 7

enthalpy change when 1 mole of electrons is added to 1 mole of gaseous atoms under standard conditions, forming 1 mole of 1- ions

Question 8

born-haber cycle

Answer 8

determine lattice enthalpy indirectly

↑ ionisation energy‍‍‍‍‍‍ ↓ electron affinity‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍
‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍ ‍‍‍‍‍‍‍‍
↑ atomisation enthalpy‍ ↓ lattice enthalpy of formation‍

↓ enthalpy of formation

Question 9

perfect ionic model

Answer 9

assume ions are 100% spherical and ionic, purely electrostatic attractions, even charge distribution

covent character: positive ions polarise neighbouring negative ions; stronger, so B-H value is greater than theoretical

Question 10

enthalpy of hydration

Answer 10

enthalpy change when 1 mole of gaseous ions become aqueous ions

Question 11

dissolving of a solid lattice

Answer 11

bonds between ions break (endo)

bonds between free ions and H2O are made (exo)

H+ bond w/ negative ions, OH- w/ positive

Question 12

enthalpy of solution

Answer 12

overall effect of dissolving

enthalpy change when 1 mole of solid ionic compound dissolves completely in an infinitely dilute solution

Question 13

enthalpy of solution cycle

Answer 13

→ enthalpy change of solution

↓ lattice dissociation enthalpy ↑enthalpy of hydration

Question 14

what happens to entropy upon dissolving

Answer 14

increases

Question 15

insoluble vs soluble

Answer 15

only dissolve if energy released > energy taken in (soluble= exo enthalpy of solution)

insoluble: lattice enthalpy > hydration enthalpy

Question 16

entropy

Answer 16

measure of disorder; no. of different ways particles can be arranged and energy can be shared between them

Question 17

entropies of vaporisation and fusion

Answer 17

vaporisation > fusion

gas is much more disordered

Question 18

enthalpy value of spontaneous reactions

Answer 18

positive

all things tend towards a state of disorder

Question 19

feasible

Answer 19

spontaneous; happen without addition of energy

Question 20

standard entropy

Answer 20

entropy of 1 mole of a substance under standard conditions

Question 21

predicting entropy change

Answer 21

increased disorder= positive entropy change

change in state

change in no. of molecules

elements in standard states do not have zero entropy

Question 22

entropy equation

Answer 22

entropy = entropy products - entropy reactants

Question 23

ΔS

Answer 23

entropy change

J K-1 mol-1

Question 24

ΔH

Answer 24

enthalpy change

KJ mol-1

Question 25

ΔG

Answer 25

Gibbs free energy change

KJ mol-1

Question 26

Gibbs equation

Answer 26

ΔG = ΔH - TΔs

Question 27

what happens if you increase entropy change/ΔS

Answer 27

creates negative enthalpy change / ΔH

this makes ΔG negative

so the reaction is always feasible

Question 28

calculate temp of feasibility or temp of phase change

Answer 28

T = ΔH / ΔS

Question 29

graph

what is y intercept?

Answer 29

ΔH / enthalpy change

Question 30

graph

what is the gradient?

Answer 30

-ΔS / negative entropy change