TEST
TOPIC 5_15
Date: 28/11/22
Time: 1hr
Max marks: 40
1. Consider the specific heat capacity of the following metals
Which metal will show the greatest temperature increase if 50 J of heat is supplied to a 0.001 kg
sample of each metal at the same initial temperature?
A. Cu
B. Ag
C. Au
D. Pt
2. When 40 joules of heat are added to a sample of solid H2O at 16.0 °C the temperature
increases to 8.0 °C. What is the mass of the solid H2O sample?
Specific heat capacity of H2O(s) = 2.0 J g-1K-1
A. 2.5 g
B. 5.0 g
C. 10 g
D. 160 g
3.The temperature of a 2.0 g sample of aluminium increases from 25 °C to 30 °C. How many
joules of heat energy were added? (Specific heat capacity of aluminium = 0.90 J g-1K-1.)
A. 0.36
B. 2.3
C. 9.0
D. 11
4. What is the energy change (in kJ) when the temperature of 20 g of water increases by 10 °C?
A. 20 × 10 × 4.18
B. 20 × 283 × 4.18
C.
D.
20 × 10 × 4.18
1000
20 × 283 × 4.18
1000
5. The ∆H values for the formation of two oxides of nitrogen are given below.
1/2 N2 (g) + O2 (g) → NO2(g)
∆H = –57 kJ mol-1
N2 (g) + 2O2 (g) → N2O4 (g)
∆H = +9 kJ mol-1
Use these values to calculate ∆H for the following reaction (in kJ):
2NO2 (g) → N2O4 (g)
A. 105
B. – 48
C. +66
D. +123
6. Approximate values of the average bond enthalpies, in kJ mol -1 , of three substances are
shown in table.
What is the enthalpy change, in kJ, for this reaction?
2HF → H2 + F2
A. +545
B. +20
C. – 20
D. – 545
7. The lattice enthalpy values for lithium fluoride and calcium fluoride are shown below.
LiF(s)
∆H = +1022 kJ mol-1
CaF2 (s)
∆H = +2602 kJ mol-1
Which of the following statements help(s) to explain why the value for lithium fluoride is less
than that for calcium fluoride?
I) The ionic radius of lithium is less than that of calcium.
II) The ionic charge of lithium is less than that of calcium.
A. I only
B. II only
C. I and II
D. Neither I nor II
8. Which reaction occurs with the largest increase in entropy?
A. Pb(NO3)2 (s) + 2KI(s) → PbI2 (s) + 2KNO3 (s)
B. CaCO3 (s) → CaO(s) + CO2 (g)
C. 3H2 (g) + N2 (g) → 2NH3 (g)
D. H2 (g) + I2 (g) → 2HI(g)
9. The ∆H and ∆S values for a certain reaction are both positive. Which statement is correct
about the spontaneity of this reaction at different temperatures?
A. It will be spontaneous at all temperatures.
B. It will be spontaneous at high temperatures but not at low temperatures.
C. It will be spontaneous at low temperatures but not at high temperatures.
D. It will not be spontaneous at any temperature.
10. The following reaction is spontaneous only at temperatures above 850° C.
CaCO3 (s) → CaO(s) + CO2 (g)
Which combination is correct for this reaction at 1000 °C?
A.
B.
C.
D.
11. Which of the following processes is exothermic?
A. Br2(l) → 2Br(g)
B. Na(g) → Na+(g) + e−
−
C. CaF2(s) → Ca2+(g) + 2F (g)
−
D. Cl(g) + e− → Cl (g)
12. Which of the following will have the largest value of lattice enthalpy?
A. NaCl
B. MgO
C. CaO
D. MgBr2
13. Use the bond enthalpies in the table to calculate the enthalpy change (in kJmol−1) for the
reaction:
CH4(g)+2Cl2(g) → CH2Cl2(g)+2HCl(g)
A. −720
B. +240
C. +620
D. −240
14. Which equation represents the lattice enthalpy of magnesium sulfide?
A. MgS (s) → Mg (g) + S (g)
–
B. MgS (s) → Mg+ (g) + S (g)
C. MgS (s) → Mg2+ (g) + S2– (g)
D. MgS (s) → Mg (s) + S (s)
15. What is the enthalpy of formation of ethyne, in kJmol−1, represented by the arrow Y on the
diagram?
A. −788−286+1301
B. −788−286−1301
C. +788+286−1301
D. +788+286+1301
16. Standard enthalpy change of combustion reactions are given below:
2C2H6 (g) + 7O2 (g) → 4CO2 (g) + 6H2O(l)
∆H = -3120 kJ
2H2(g) + O2 (g) → 2H2O(l)
∆H = -572 kJ
C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O(l)
ΔH = -1411 kJ
a) Based on the above information, calculate the standard change in enthalpy, ∆H , for the
following reaction: [2]
C2H6 (g) → C2H4 (g) + H2 (g)
b) Predict, stating a reason, whether the sign of ∆S for the above reaction would be positive or
negative. [2]
c) Calculate the standard entropy change for the reaction. [2]
d) Determine the value of ∆G for the reaction at 298 K. [2]
e) Determine the temperature at which this reaction will occur spontaneously. [2]
[Total 10 marks]
17. Hydrazine, N2H4, has been used as a rocket fuel.
a) Draw a Lewis structure for hydrazine. [1]
b) Write a chemical equation to represent the enthalpy change of formation of gaseous
hydrazine. [2]
c) Use bond enthalpies from the table to calculate the enthalpy change of formation of gaseous
hydrazine. [3]
d) The equation for the combustion of liquid hydrazine is:
N2H4(l) + O2(g) → N2(g) + 2H2O(l)
∆H=−622 kJmol−1
The enthalpy change of formation of H2O(l) is −286 kJmol−1. Use these data to calculate the
enthalpy change of formation of liquid hydrazine. [3]
e) Calculate the enthalpy change for the process: [2]
N2H4(l) → N2H4(g)
[Total 11 marks]
18. The standard enthalpy change of three combustion reactions is given below in kJ.
2C2H6 (g) + 7O2 (g) → 4CO2 (g) + 6H2O(l)
∆H = –3120
2H2 (g) + O2 (g) → 2H2O(l)
∆H = –572
C2H4 (g) + 3O2 (g) → 2CO2(g) + 2H2O(l)
∆H = –1411
Based on the above information, calculate the standard change in enthalpy, ∆H , for the
following reaction.
C2H6 (g) → C2H4 (g) + H2 (g)
[4]