End of topic test: Energetics
Higher level
PAPER 1 QUESTIONS
1. This cycle may be used to calculate the enthalpy of 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
2. How would this reaction at 298K be described in thermodynamic terms:
H2O(l) → H2(g) + O2(g)
A. Endothermic with a significant increase in entropy
B. Endothermic with a significant decrease in entropy
C. Exothermic with a significant increase in entropy
D. Exothermic with a significant decrease in entropy
3. Use the data below to calculate the enthalpy of formation of carbon monoxide in kJ mol-1
A. 
B. 
C. 
D. 
C(s) + O2(g) → CO2(g) ∆Hᶿ = -393KJ
2CO(g) O2(g) → 2CO2(g) ∆Hᶿ = -588KJ
4. The equation for the hydrogenation of ethene is given:
C2H4 (g) + H2(g) → C2H6(g) ∆H = -137 kJ
Which statement about the information above is correct?
A. The total energy of the bonds broken in the reactants is greater than the total energy of
the bonds formed in the product
B. The bonds broken and the bonds made are of the same strength
C. The total energy of the bonds broken in the reactants is less than the total energy of the
bonds formed in the product
D. No conclusion can be made about the sums of the bond enthalpies in the product
compared with the reactants.
5. When solid ammonium nitrate, NH4NO3(s) dissolves in water, the temperature decreases.
Which statement about the dissolving of ammonium nitrate in water is correct?
A. It is endothermic with ∆H greater than zero.
B. It is endothermic with ∆H less than zero.
C. It is exothermic with ∆H less than zero.
D. It is exothermic with ∆H greater than zero.
6. Which change leads to a decrease in entropy for the system?
A. Solid ammonium chloride sublimes.
B. Sodium corrodes in air.
C. Potassium nitrate dissolves in water.
D. Two inert gases mix at constant temperature and pressure.
7. A certain reaction is spontaneous at low temperatures but becomes non-spontaneous as the
temperature is raised. Based on this information, what are the signs of ∆Hᶿ and ∆Sᶿ?
A
B
C
D
∆Hᶿ
+
+
-
∆Gᶿ
+
+
-
8. When 40 joules of heat are added to a sample of solid H2O at -16.0 OC the temperature
increases to -8.0 OC. What is the mass of the solid H2O sample?
[Specific heat capacity of H2O(s) = 2.0 Jg-1K-1]
A. 2.5 g
B. 5.0 g
C. 10 g
D. 160 g
9. The ∆Hᶿ values for the formation of two oxides of nitrogen are given below.
½ N2(g) + O2(g) → NO2(g)
N2(g) + 2O2(g) → N2O4(g)
∆Hᶿ = -57 KJmol-1
∆Hᶿ = +9 KJmol-1
Use these values to calculate ∆H (in kJ) for the following reaction
2 NO2(g) → N2O4(g)
A. –105
B. – 48
C. +66
D. +123
10. Which combination of ion charge and ion size produces the greatest lattice enthalpy?
A. High charge, large size
B. High charge, small size
C. Low charge, small size
D. Low charge, large size
11. Which process represents the C–Cl bond enthalpy in tetrachloromethane?
A. CCl4(g) → C(g) + 4Cl(g)
B. CCl4(g) → CCl3(g) + Cl(g)
C. CCl4(l) → C(g) + Cl(g)
D. CCl4(l) → C(s) + 2Cl2(g)
12. Which reaction has the greatest increase in entropy?
A. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
B. H2(g) Cl2(g) → 2HCl(g)
C. N2(g) 3H2(g) → 2NH3(g)
D. C2H4(g) + H2(g) → C2H6(g)
13. The reaction between but-1-ene and water vapour produces butan-1-ol.
C4H8(g) H2O(g) → C4H9OH(l)
The standard entropy values (Sᶿ) for but-1-ene, water vapour and butan-1-ol are 310, 189 and
228 JK-1mol-1 respectively. What is the entropy change for this reaction in JK-1mol-1?
A. –271
B. +271
C. –107
D. +107
14. A reaction has a standard enthalpy change, ∆Hᶿ, of +10.00 kJmol-1 at 298 K. The
standard entropy change, ∆Sᶿ, for the same reaction is +10.00 JK-1mol-1. What is the value of
∆Gᶿ for the reaction in kJ mol-1?
A. +9.75
B. +7.02
C. –240
D. –2970
15. Which process is exothermic?
A. Na(s) → Na(g)
B. Ca(g) → Ca+(g) + eC. Br(g) + e- → Br-(g)
D. I2(g) → 2I(g)
16. Which equation represents the standard enthalpy of formation of calcium fluoride?
A. Ca(g) + F2(g) → CaF2(g)
B. Ca(s) + F2(g) → CaF2(g)
C. Ca2+(g) + 2F-(g) → CaF2(s)
D. Ca2+(s) + 2F-(g) → CaF2(s)
17. Which of the following is correct about the energy changes during bond breaking and
bond formation?
A
B
C
D
Bond breaking
Exothermic
Exothermic
Endothermic
Endothermic
Bond formation
Endothermic
Exothermic
Endothermic
Exothermic
18. What should be the signs of ∆G, ∆H and ∆S for a chemical reaction to be spontaneous at
any temperature?
A
B
C
D
∆G
Positive
Negative
Negative
Negative
∆H
Negative
Negative
Negative
Positive
∆S
Positive
Negative
Positive
Negative
19. Which statement is correct for an endothermic reaction?
A. Bonds in the products are stronger than the bonds in the reactants.
B. Bonds in the reactants are stronger than the bonds in the products.
C. The enthalpy of the products is less than that of the reactants.
D. The reaction is spontaneous at low temperatures but becomes non-spontaneous at high
temperatures.
20. Consider the following information.
Which expression gives the correct value of the standard enthalpy change of combustion for
benzene (l), in kJ mol-1?
A.
B.
C.
D.
12(-394)+6(-286)-2(49)
12(394)+6(286)-2(-49)
6(-394)+3(-286)-(49)
6(394)+3(286)-(-49)
PAPER 2 QUESTIONS
21 (a) (i) Define the term standard enthalpy of formation. [2]
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(ii) Write an equation, including state symbols, to show the formation of propane. [1]
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(b) (i) State what is meant by the term average bond enthalpy. Use the average bond
enthalpies, provided in the Data Booklet (Table 10), to calculate the enthalpy change (∆Hᶿ )
for the following reaction: [5]
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
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(ii) Suggest, with a reason, whether the entropy change (∆Sᶿ) for the reaction would be
positive or negative. [2]
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22 The enthalpy diagram for a reaction between two aqueous solutions at room temperature
is shown
(a) Complete the graph by drawing a curve to link the reactants and products. Label the
enthalpy change, ∆H, and the activation energy EA [3]
(b) Give the sign of ∆Hᶿ for this reaction and indicate whether it is endothermic or
exothermic. State the relative strengths of the bonds in the products and reactants. [5]
(c) This reaction is spontaneous at room temperature. Use this information along with that in
(i) to give the signs of ∆Gᶿ and ∆Sᶿ, outlining your reasoning in each case. Comment on the
meaning of the sign of ∆Sᶿ in terms of the relative disorder of the reactants and products. [6]
23. The standard enthalpy of combustion, ∆Hcᶿ, and the relative molecular masses, Mr, of a
series of alcohols are given below:
(a) (i) Calculate the relative molecular mass of pentan-1-ol and thus estimate for ∆Hcᶿ
pentan-1-ol using the graph below. [2]
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(ii) How would the value of the standard enthalpy of combustion of pentan-2-ol compare
with that of pentan-1-ol? Explain your reasoning. [2]
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(b) The reaction between methanol and oxygen is spontaneous at all temperatures. Explain
why methanol vapour is stable in air, but the mixture reacts quickly when ignited. [2]
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(c) (i) 10.0 g of solid NaOH is added to 100 g of water at 23.2 oC in a glass beaker. The
solution is stirred and a maximum temperature of 44.6oC is reached. Calculate the heat
produced by the reaction. (Assume the specific heat capacity of the solution is 4.20 Jg -1oC-1 .)
[3]
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(ii) Calculate the enthalpy change for dissolving solid NaOH in water (in kJmol -1). [1]
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(iii) The value given in the literature under similar conditions is -42.7kJmol-1 . Suggest a
reason why the calculated value of the enthalpy change of solution is different from the
literature value and propose an improvement in the procedure to obtain a more accurate
value. [2]
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24. The following enthalpy changes refer to sodium chloride (in kJ mol-1) and its constituent
elements.
(a) (i) State the meaning of the + and – signs in the enthalpy values. [1]
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(ii) Explain the meaning of the symbol ᶿ. [1]
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(b) Write an equation, including state symbols, for each of the above enthalpy changes. [5]
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(c) The given values can be used to calculate the lattice enthalpy of sodium chloride.
(i) Define the term lattice enthalpy. [1]
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(ii) Construct a Born-Haber cycle and hence calculate the lattice enthalpy of sodium
chloride. [4]
Appendix
Questions taken or adapted from
Q1 November 1999 paper1 Q18
Q2 November 1999 paper1 Q21
Q3 November 2000 paper1 Q18
Q4 November 2000 paper1 Q19
Q5 November 2001 paper1 Q17
Q6 November 2001 paper1 Q19
Q7 November 2001 paper1 Q20
Q8 November 2007 paper1 Q15
Q9 November 2007 paper1 Q16
Q10 November 2007 paper1 Q18
Q11 May 2009 paper1.1 Q15
Q12 May 2009 paper1.1 Q16
Q13 May 2009 paper1.1 Q17
Q14 May 2009 paper1.1 Q18
Q15 May 2008 paper1.1 Q18
Q16 May 2008 paper1.1 Q19
Q17 May 2008 paper1.2 Q18
Q18 May 2008 paper1.2 Q19
Q19 May 2007 paper1 Q16
Q20 May 2007 paper1 Q17
Q21 May 2001 paper2 Q3
Q22 May 2000 paper2 Q7(a)
Q23 Nov 2001 paper2 Q1
Q24 Nov 2002 paper2 Q1