Thermodynamics

Question 1

enthalpy of lattice formation

Answer 1

the enthalpy change when one mole of a solid ionic lattice is formed from its gaseous ions

Question 1

enthalpy of atomisation

Answer 1

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

Question 2

standard enthalpy of combustion

Answer 2

the enthalpy change when 1 mole of a compound is burned completely in oxygen under standard conditions with all reactants and products in their standard states

Question 3

standard enthalpy of formation

Answer 3

the enthalpy change when 1 mole of a compound is formed from its constituent elements under standard conditions with all reactants and products in their standard states

Question 4

first ionisation energy

Answer 4

the enthalpy change when one mole of gaseous 1+ ions is formed from one mole of gaseous atoms

Question 5

first electron affinity

Answer 5

the enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole of gaseous atoms

Question 6

enthalpy of hydration

Answer 6

the enthalpy change when 1 mole of aqueous ions is formed from 1 mole of gaseous ions

Question 7

bond dissociation enthalpy

Answer 7

the enthalpy change when all the bonds of the same type are broken in 1 mole of gaseous molecules

Question 8

enthalpy change of solution

Answer 8

the enthalpy change when 1 mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution

Question 9

lattice enthalpy of dissociation

Answer 9

the enthalpy change when 1 mole of a solid ionic compound is completely dissociated into its gaseous ions under standard conditions

Question 10

what are born haber cycles used for

Answer 10

to calculate lattice enthalpies

Question 11

give the equation for the enthalpy of atomisation of chlorine

Answer 11

½Cl₂ (g) → Cl (g)

Question 12

give the equation for the first electron affinity of oxygen

Answer 12

O + e- (g) → O- (g)

Question 13

give the equation for the second electron affinity of oxygen

Answer 13

O- + e- (g) → O2- (g)

Question 14

give the equation for the enthalpy change of solution of NaCl

Answer 14

NaCl (s) → NaCl (aq)

Question 15

give the equation for the enthalpy change of hydration of sodium

Answer 15

Na+ (g) → Na+ (aq)

Question 16

give the equation for the bond dissociation enthalpy of chlorine

Answer 16

Cl₂ (g) → 2Cl (g)

Question 17

how to calculate the temperature at which a reaction becomes feasible

Answer 17

T = ΔH/ΔS

Question 18

what is the difference between covalent and ionic compounds (in terms of electrons)?

Answer 18

covalent = electrons are shared

ionic = electrons are transferred

Question 19

what is the effect of covalent character on lattice values?

Answer 19

it makes them higher

Question 20

which takes into account covalent character, the theoretical value or the experimental value?

Answer 20

experimental (from born-haber cycles)

theoretical values are based on a perfect ionic model