SECTION A: Multiple choice
1. (N06) Which statement is correct for an endothermic reaction?
A. The products are more stable than the reactants and ΔH is positive.
B. The products are less stable than the reactants and ΔH is negative.
C. The reactants are more stable than the products and ΔH is positive.
D. The reactants are less stable than the products and ΔH is negative.
2. (N06) Which equation represents an exothermic process?
A. F- (g)  F (g) + eB. F2 (g)  2F (g)
C. Na (g)  Na+ (g) + eD. I2 (g)  I2 (s)
3. (N05) The following equation shows the formation of magnesium oxide from magnesium metal.
Which statement is correct for this reaction?
A. 1204kJ of energy are released for every mol of magnesium reacted.
B. 602kJ of energy are absorbed for every mol of magnesium oxide formed.
C. 602kJ of energy are released for every mol of oxygen gas reacted.
D. 1204kJ of energy are released for every two mol of magnesium oxide formed.
4. (N05) The following equations show the oxidation of carbon and carbon monoxide to
carbon dioxide.
What is the enthalpy change, in kJ mol-1 , for the oxidation of carbon to carbon monoxide?
A. x
y
B. – x - y
C. y – x
D. x – y
1
5. (N05) A simple calorimeter was used to determine the enthalpy of combustion of ethanol.
The experimental value obtained was -920kJ mol-1. The Data Booklet value is -1371kJ mol-1. Which
of the following best explains the difference between the two values?
A. incomplete combustion of the fuel.
B. heat loss to the surroundings.
C. poor ventilation in the laboratory.
D. inaccurate temperature measurements.
6. (M06) Which statement about bond enthalpies is correct?
A. Bond enthalpies have positive values for strong bonds and negative values for weak bonds.
B. Bond enthalpy values are greater for ionic bonds than for covalent bonds.
C. Bond breaking is endothermic and bond making is exothermic.
D. The carbon–carbon bond enthalpy values are the same in ethane and ethene.
7. (M06) An equation for a reaction in which hydrogen is formed is
Which energy change occurs when 1 mol of hydrogen is formed in this reaction?
A. 0 kJ of energy are absorbed from the surroundings.
B. 0 kJ of energy are released to the surroundings.
C. 210 kJ of energy are absorbed from the surroundings.
D. 210 kJ of energy are released to the surroundings.
8. (M06) The equations and enthalpy changes for two reactions used in the manufacture of
sulfuric acid are:
What is the enthalpy change, in kJ mol-1 , for the reaction below?
A. –100
B. –400
C. –500
D. –800
2
9. Given the equations
N2 (g) + 2O2 (g)  2NO2 (g)
NO (g) + ½O2 (g)  NO2 (g)
H = 66.4 kJ
H = -57.1 kJ
calculate H for the reaction
N2 (g) + O2 (g)  2NO (g)
A. 47.8 kJ
B. 90.3 kJ
H =
C. 123.5 kJ
D. 180.6 kJ
H
10.
2HCl (aq) + 2 KHCO3 (s)
K2CO3 (s) + CO2 (g) + H2O (l)
H1
H2
+ 2HCl (aq)
2 KCl (aq) + 2 CO2 (aq) + 2 H2O (l)
This cycle may be used to determine H for the decomposition of potassium hydrogen carbonate.
Which expression can be used to calculate H?
A. H = H1 + H2
B. H = H1 - H2
C. H = ½ H1 - H2
D. H = H2 - H1
11. The bond enthalpy for F2 (g) = 153 kJ mol-1 and that for H2 (g) = 436 kJ mol-1. Use these
values and H for the reaction below to calculate the bond enthalpy for the HF bond in kJ
mol-1.
F2 (g) + H2 (g)  2HF (g)
H = -521 kJ
A. 1110
B. 555
C. 136
D. 68
12. Which statement about this reaction is correct?
2Fe (s) + 3CO2 (g) 
Fe2O3 (s) + 3CO (g)
H = + 26.6 kJ
A. 26.6 kJ of energy are released for every mole of Fe reacted
B. 26.6 kJ of energy are absorbed for every mole of Fe reacted
C. 53.2 kJ of energy are released for every mole of Fe reacted
D. 13.3 kJ of energy are absorbed for every mole of Fe reacted
13. Which reaction has an enthalpy change equal to four times the bond enthalpy of the C-H bond?
A. CH4(g)  C (s) + 2H2 (g)
B. CH4(g)  C (g) + 2H2 (g)
C. CH4(g)  C (s) + 4H (g)
D. CH4(g)  C (g) + 4H (g)
3
14. When 50.0 cm3 of 1 mol dm-3 HCl is mixed with 50 cm3 of 1 mol dm-3 NaOH, the temperature of the
resulting solution increases by 6C. What will be the temperature change when 100 cm-3 of each of
these solutions are mixed?
A. 3C
B. 6C
C. 12C
D. 24C
15. Given the following equations
N2 (g) + 2O2 (g)  2NO2 (g)
2NO (g) + O2 (g)  2NO2 (g)
H = 66.4 kJ
H = -114.0 kJ
Calculate H for the reaction
N2 (g) + O2 (g)  2NO (g)
A. -47.8 kJ
B. 47.8 kJ
H =
C. 90.3 kJ
D. 180.4 kJ
16. What is the value of H (in kJ mol-1) for the reaction below?
H
H
C=C
H
Bond energies
(in kJ mol-1)
A. 124
+ H2

H
H
H
H
C
C
H
H
H-H
436
C-C
348
B. 101
C. –101
H
C=C
612
C-H
412
D. -124
SECTION B
1. (N06) Methylamine can be manufactured by the following reaction.
(a) Define the term average bond enthalpy.
[2]
(b) Use information from Table 10 of the Data Booklet to calculate the enthalpy change for
this reaction.
[4]
2. (N05)
(a) Two reactions occurring in the manufacture of sulfuric acid are shown below:
4
(i) State the name of the term ∆H . State, with a reason, whether reaction I would be
accompanied by a decrease or increase in temperature.
[3]
(ii) At room temperature sulfur trioxide, SO3, is a solid. Deduce, with a reason, whether the ∆H
value would be more negative or less negative if SO3 (s) instead of SO3 (g) were formed in
reaction II.
[2]
(iii) Deduce the ∆H value of this reaction:
(b) (i) Explain why Br2 is not suitable as an example to illustrate the term average bond
enthalpy.
(ii) Using values from Table 10 of the Data Booklet, calculate the enthalpy change for the
following reaction:
(iii) Sketch an enthalpy level diagram for the reaction in part (b) (iii).
[1]
[3]
[3]
[2]
(iv) Without carrying out a calculation, suggest, with a reason, how the enthalpy change
for the following reaction compares with that of the reaction in part (b) (iii):
3. (M06) But–1–ene gas, burns in oxygen to produce carbon dioxide and water vapour according to the
following equation
(a) Use the data below to calculate the value of for the combustion of but-1-ene.
[3]
(b) State and explain whether the reaction above is endothermic or exothermic.
[1
(c) Calculate the enthalpy change, for the reaction
[4]
using Hess’s Law and the following information
5
Marks scheme
SECTION A
1
2
3
4
C
D
D
C
5
6
7
8
B
C
B
D
9
10
11
12
D
B
B
D
13
14
15
16
D
B
D
D
17
18
19
20
SECTION B
1. (N06)
2.
6
3. (M06)
7
8