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LSM 11.2C
Solutions for Bomb Calorimetry,
Extra Exercise (Extension)
1. An oxygen bomb calorimeter has a heat capacity of 6.49 kJ/qC. The complete combustion of
1.12 g of ethyne, C2H2(g), produces a temperature change from 18.60 qC to 27.15 qC.
Calculate the molar enthalpy of combustion, 'cHm, for ethyne.
C = 6.49 kJ/°C
ǻt = 27.15 - 18.60 °C = 8.55 °C
1 mol
nC2 H2 = 1.12 g ×
= 0.0430 mol
26.04 g
Q = C ǻt
= 6.49 kJ/°C × 8.55 °C
= 55.4895 kJ
ǻc H = Q = 55.4895 kJ
55.4895 kJ
= 1290 kJ/mol or 1.29 mJ/mol
0.0430 mol
The reaction is exothermic, so the molar enthalpy of combustion for ethyne is
–1.29 mJ/mol.
ǻc H mol =
2. Canadian inventors have developed zeolite, a natural aluminium silicate mineral, as a storage
medium for solar heat. Zeolite releases heat when hydrated with water. In a test, zeolite is
used to heat water in a tank that has a heat capacity of 157 kJ/qC. What is the enthalpy change
of hydration ('Hh) for zeolite if the temperature of the water increases from 27 qC to 73 qC?
C = 157 kJ/°C
ǻt = 73 - 27 °C = 46 °C
Q = C ǻt
= 157 kJ/°C × 46 °C
= 7200 kJ
ǻh H = Q = 7200 kJ or 7.2 mJ
The reaction is exothermic, so the enthalpy change of hydration for zeolite is –7.2 mJ.
3. Besides the molar enthalpy of combustion as determined in a bomb calorimeter, what other
properties or factors are involved in evaluating automobile fuels such as propane, ethanol,
and hydrogen?
Properties or factors to consider include:
Ɣ availability
Ɣ effectiveness as a fuel
Ɣ cost of production
Ɣ ease of distribution and storage
Ɣ acceptance by consumers
Ɣ impact on the environment
Copyright © 2007 Thomson Nelson
Unit 6 Lab and Study Masters
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