3.1.8 - thermodynamics

Question 1

Enthalpy change of formation (∆fHƟ)

Answer 1

the enthalpy change when 1 mole of a
compound is formed from its constituent elements in their standard
states, under standard conditions.
* E.g. 2C(s) + 3H2(g) + ½O2(g) → C2H5OH(l)

Question 2

Enthalpy change of combustion (∆cHƟ)

Answer 2

the enthalpy change when 1 mole of
a substance is completely burned in O2 under standard conditions with all
reactants + products in their standard states.
* E.g. CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)

Question 3

Bond dissociation enthalpy (∆BDEHƟ):

Answer 3

the enthalpy change when 1 mole of bonds of the same type are broken under standard conditions in the gaseous state.
* E.g. Cl2(g) → 2Cl(g)

Question 4

Enthalpy change of atomisation (∆atHƟ)

Answer 4

the enthalpy change for the
formation of 1 mole of gaseous atoms from the element/compound in its
standard state.
* E.g. NaCl(s) → Na(g) + Cl(g

Question 5

First ionisation enthalpy (∆ie1HƟ)

Answer 5

enthalpy change when 1 mole of
electrons is removed from 1 mole of gaseous atoms to form one mole of
gaseous ions with a +1 charge.
* E.g. Na(g) → Na+(g) + e

Question 6

Second ionisation enthalpy (∆ie2HƟ)

Answer 6

enthalpy change when 1 mole of
electrons is removed from 1 mole of gaseous ions with a charge of +1 to
form one mole of gaseous ions with a
charge of +2.
* E.g. Na+(g) → Na2+(g) + e

Question 7

First electron affinity (∆EA1HƟ)

Answer 7

enthalpy change when 1 mole of gaseous
atoms form 1 mole of gaseous ions w/ a charge of -1.
* E.g. O(g) + e- → O-(g)

Question 8

values of first electron affinity are negative bc

Answer 8

process is exothermic

Question 9

.
Second electron affinity (∆EA2HƟ)

Answer 9

enthalpy change when 1 mole of gaseous
ions with a charge of -1 form 1 mole of gaseous ions with a charge of -2.
* E.g. O-(g) + e- → O2-(g)

Question 10

whats significant ab second electron affinity value and why is this the case

Answer 10

Values of second electron affinities are +ve as the process is
endothermic.
- This is due to the repulsion from the negative ion toward the
negative electron being added.

Question 11

Enthalpy of lattice dissociation (∆LHƟ)

Answer 11

the enthalpy change when 1 mole
of an solid ionic compound is dissociated into its constituent gaseous ions under standard conditions
* E.g. NaCl(s) → Na+(g) + Cl-(g)

Question 12

Enthalpy of lattice formation (∆LHƟ)

Answer 12

the enthalpy change when 1 mole of
an ionic compound is formed from its gaseous ions.
* E.g. Na+(g) + Cl-(g) → NaCl(s)

Question 13

Enthalpy of hydration (∆hydHƟ):

Answer 13

the enthalpy change when 1 mole of gaseous
ions is converted into 1 mole of aqueous ions.
* E.g. Na+(g) → Na+(aq)

Question 14

Enthalpy of solution (∆solHƟ)

Answer 14

the enthalpy change when 1 mole of an ionic
substance dissolves in enough solvent to form an infinitely dilute
solution.