Define the term standard enthalpy change of formation, ΔH°f.
Using the following data, calculate the standard enthalpy change of combustion of ethanol, C₂H₅OH.
ΔH°f [C₂H₅OH(l)] = −278 kJ mol⁻¹
ΔH°f [CO₂(g)] = −394 kJ mol⁻¹
ΔH°f [H₂O(l)] = −286 kJ mol⁻¹
[6 marks]
Mathematics
Edexcel2023
Mg2+(aq) + 2Cl–(aq)
The enthalpy changes of hydration of the ions are:
Mg2+ −1920 kJ mol–1
Cl– −364 kJ mol–1
Calculate the enthalpy change of solution, ΔH , of MgCl (s) in kJ mol–1.
solution 2
(2)
Question
Mathematics
Edexcel2023
ΔHd / kJ mol–1 ΔSd / J K–1 mol–1
solution system
–87 –210
(i) Explain why the dissolving of magnesium sulfate in water is exothermic by
considering the enthalpy changes involved.
(2)
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
(ii) Use the data in the table to calculate ΔGd when magnesium sulfate dissolves
in water at 298 K. State the significance of your answer.
(2)
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
Question
Mathematics
Edexcel2022
This question is about enthalpy changes and energy changes.
(a) Magnesium carbonate reacts with dilute hydrochloric acid at room temperature.
MgCO (s) + 2HCl(aq) → MgCl (aq) + CO (g) + H O(l)
Question
Mathematics
Edexcel2021
*P65463A02428*
PPMMTT
(b) Data for the Born-Haber cycle for copper(II) oxide are given in the table.
Label Energy change Value / kJ mol–1
A standard enthalpy change of atomisation of copper +338
B standard enthalpy change of atomisation of oxygen +249
C sum of first and second ionisation energies of copper +2704
D first electron affinity of oxygen –141
E second electron affinity of oxygen +798
F standard enthalpy change of formation of copper(II) oxide –157
(i) Complete the diagram of the Born-Haber cycle for copper(II) oxide.
Include labels of enthalpy changes with arrows indicating the direction of
change, and the respective species with state symbols.
(4)
Cu(s) + ½O (g)
Question
Mathematics
Edexcel2017
This question is about enthalpy changes and entropy changes.
(a) Which is the equation for the standard enthalpy change of formation, (cid:168) H ,
f
of aluminium oxide?
(1)
A 4Al(s) + 3 O (g) (cid:114) 2Al O (s) 2 2 3
B 4Al(s) + 6 O(g) (cid:114) 2Al O (s)
Question
Mathematics
Edexcel2017
*P48058A01428*
DO
NOT
WRITE
IN
THIS
AREA
DO
NOT
WRITE
IN
THIS
AREA
DO
NOT
WRITE
IN
THIS
AREA
(b) The table shows the enthalpy changes needed to calculate the first electron affinity
of bromine.
Value
Enthalpy change
/ kJ mol–1
enthalpy change of atomisation of magnesium, (cid:168) H [Mg(s)] +148
at
1st ionisation energy of magnesium, 1st IE[Mg(g)] +738
2nd ionisation energy of magnesium, 2nd IE[Mg+(g)] +1 451
enthalpy change of atomisation of bromine, (cid:168) H [½Br (l)] +112 at 2
lattice energy of magnesium bromide, LE[MgBr (s)] –2 440
Question
Mathematics
Edexcel2017
*P48058A01728*
Turn over
AERA
SIHT
NI
ETIRW
TON
OD
AERA
SIHT
NI
ETIRW
TON
OD
AERA
SIHT
NI
ETIRW
TON
OD
*( b) The table shows the enthalpy changes of reaction when 1 mol of different acids
are neutralised by sodium hydroxide solution, at 298 K.
Enthalpy change of reaction
Acid
for 1 mol of acid / kJ mol–1
hydrochloric acid, HCl –58
nitric acid, HNO –58
Question
Mathematics
Edexcel2017
Comment on the relative enthalpy changes of reaction, using the data from the
table and including any relevant equations.
(6)
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
.....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
....................................................................................................................................................................................................................................................................................
(Total for Question 7 = 9 marks)