Untitled - Kelly Walsh High School

106 CHEMISTRY FOR THE UTTERLY CONFUSED
8. Calculate the standard heat of formation for HC 2H 3O 2(l) using the following:
C(s) O 2(g) l CO 2(g) H 393.5 kJ
H 2(g) 1/2 O 2(g) l H 2O(l) H 285.8 kJ
HC 2H 3O 2(l) 2O 2(g) l 2 CO 2(g) 2H 2O(l) H 871 kJ
The reaction for the standard heat of formation of HC 2H 3O 2(l) is:
2 C(s) 2 H 2(g) O 2(g) l HC 2H 3O 2(l)
9. Calculate the heat of reaction for: 2N 2(g) 5O 2(g) l 2N 2O 5(g) using the
following thermochemical equations:
N 2(g) 3 O 2(g) H 2(g) l 2 HNO 3(aq) H 413.14 kJ
N 2O 5(g) H 2O(g) l 2 HNO 3(aq) H 218.4 kJ
2 H 2(g) O 2(g) l 2 H 2O(g) H 483.64 kJ
10. Propane gas, C 3H 8, is sometimes used as a fuel. In order to measure its
energy output as a fuel a 1.860 g sample was combined with an excess of O 2
and ignited in a bomb calorimeter. After the reaction, it was found that the
temperature of the calorimeter had increased from 25.000C to 26.061C.
The calorimeter contained 1.000 kg of water. The heat capacity of the
calorimeter was 4.643 kJ/C. Determine the heat of reaction, in kJ/mol
propane. The reaction was:
C 3H 8(l) 5 O 2(g) l 3 CO 2(g) 4 H 2O(l)
ANSWER KEY
1. False 2. False 3. True 4. True 5. True
6. 1 J 1 kgm2 /s2 10. 222.0 kJ/mol
7. J/gK (or J/gC) 8. 488 kJ 9. 779.4 kJ