1. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
PCl5(g) → PCl3(g) + Cl2(g)
P4(s) + 6Cl2(g) → 4PCl3(g)
4PCl5(g) → P4(s) + 10Cl 2(g)
ΔH = -2439 kJ
ΔH = 3438 kJ
2. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
2CO2(g) + H2O(g) → C 2H2(g) + 5/2O2(g)
C2H2(g) + 2H2(g) → C2H6(g)
H2O(g) → H2(g) + 1/2O2 (g)
C2H6(g) + 7/2O2(g) → 2CO2(g) + 3H2O(g)
ΔH =-94.5 kJ
ΔH =71.2 kJ
ΔH =-283 kJ
3. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
N2H4(l) + H2(g) → 2NH3(g)
N2H4(l) + CH4O(l) → CH2O(g) + N2(g) + 3H2 (g)
N2(g) + 3H2(g) → 2NH 3(g)
CH4O(l) → CH2O(g) + H 2(g)
ΔH = -37 kJ
ΔH = -46 kJ
ΔH = -65 kJ
4. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
H2SO4(l) → SO3(g) + H2O(g)
H2S(g) + 2O2(g) → H2SO4(l)
H2S(g) + 2O2(g) → SO 3(g) + H2O(l)
H2O(l) → H2O(g)
ΔH = -235.5 kJ
ΔH = -207 kJ
ΔH = 44 kJ
5. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
2C2H4O(l) + 2H2O(l) → 2C2H6O(l) + O2(g)
C2H6O(l) + 3O2(g) → 2CO2(g) + 3H2O(l)
C2H4O(l) + 5/2O2(g) → 2CO2(g) + 2H2O(l)
ΔH = -685.5 kJ
ΔH = -583.5 kJ
6. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
N2(g) + 2O2(g) → 2NO 2(g)
N2(g) + 3H2(g) → 2NH3(g)
2NH3(g) + 4H2O(l) → 2NO2(g) + 7H2(g)
H2O(l) → H2(g) + 1/2O 2(g)
ΔH = -115 kJ
ΔH = -142.5 kJ
ΔH = -43.7 kJ
7. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
CO2(g) → C(s) + O2(g)
H2O(l) → H2(g) + 1/2O2(g)
C2H6(g) → 2C(s) + 3H 2(g)
2CO2(g) + 3H2O(l) → C 2H6(g) + 7/2O2(g)
ΔH = 643 kJ
ΔH = 190.6 kJ
ΔH = 3511.1 kJ
8. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
N2H4(l) + CH4O(l) → CH2O(g) + N2(g) + 3H2 (g)
2NH3(g) → N2H4(l) + H2(g)
2NH3(g) → N2(g) + 3H 2(g)
CH2O(g) + H2(g) → CH 4O(l)
ΔH = 22.5 kJ
ΔH = 57.5 kJ
ΔH = 81.2 kJ
9. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
1/2H2(g) + 1/2Cl2(g) → HCl(g)
COCl2(g) + H2O(l) → CH2Cl2(l) + O2(g)
2HCl(g) + 1/2O2(g) → H 2 O(l) + Cl2(g)
CH2Cl2(l) + H2(g) + 3/2O 2(g) → COCl2(g) + 2H 2O(l)
ΔH = 47.5 kJ
ΔH = 105 kJ
ΔH = -402.5 kJ
10. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
C2H2(g) + 5/2O2(g) → 2CO2(g) + H2O(g)
C2H6(g) → C2H 2(g) + 2H2(g)
H2(g) + 1/2O2(g) → H2O(g)
2CO2(g) + 3H2O(g) → C2H6(g) + 7/2O2(g)
ΔH = 283.5 kJ
ΔH = -213.7 kJ
ΔH = 849 kJ
11. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
HCl(g) + NaNO2(s) → HNO2(l) + NaCl(s)
2NaCl(s) + H2O(l) → 2HCl(g) + Na2O(s)
NO(g) + NO2(g) + Na2O(s) → 2NaNO2(s)
NO(g) + NO2(g) → N2O(g) + O2(g)
2HNO2(l) → N2O(g) + O2(g) + H 2O(l)
ΔH = 507 kJ
ΔH = -427 kJ
ΔH = -43 kJ
ΔH = 34 kJ
12. Find the ΔH for the reaction below, given the following reactions and subsequent ΔH values:
Zn(s) + 1/8S8(s) + 2O2(g) → ZnSO4(s)
Zn(s) + 1/8S8(s) → ZnS(s)
2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g)
2SO2(g) + O2(g) → 2SO3(g)
ZnO(s) + SO3(g) → ZnSO4 (s)
ΔH = -183.92 kJ
ΔH = -927.54 kJ
ΔH = -196.04 kJ
ΔH = -230.32 kJ
13. Given the following equations:
4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (l) ΔH= -1170 kJ
4 NH3 (g) + 3 O2 (g) → 2 N2 (g) + 6 H2O (l) ΔH= -1530 kJ
Using these two equations, determine the heat of formation of nitrogen monoxide, NO.
14.
H3BO3(aq)
HBO2(aq) + H2O(l) ΔH = -0.02 kJ
H2B4O7(aq) + H 2O(l)
4HBO2(aq) ΔH = -11.3 kJ
H2B4O7(aq)
2B2O3(s) + H2O(l) ΔH = 17.5 kJ
find the ΔH for this overall reaction:
2H3BO3(aq)
B2O3(s) + 3H2O(l)
15.
2 C (s)  2 H2O (g)  CH4 (g)  CO2(g)
Determine the standard enthalpy change for this reaction from the following
standard enthalpies of reaction :
(1) C(s)  H2O (g)  CO (g)  H2 (g)
H  131.3 kJ
(2) CO (g)  H2O (g)  CO2 (g)  H2 (g)
(3) CH4 (g)  H2O (g)  3 H2 (g)  CO (g)
H  - 41.2 kJ
H  206.1 kJ
16. One reaction involved in the conversion of iron ore to the metal is
FeO (s)  CO (g)  Fe (s)  CO2 (g)
Calculate the standard enthalpy change for this reaction from these reactions
of iron oxides with CO :
(1) 3 Fe2O3 (s)  CO (g)  2 Fe3O4 (s)  CO2 (g)
(2) Fe2O3 (s)  3 CO (g)  2 Fe (s)  3 CO2 (g)
H  - 47.0 kJ
H  - 25.0 kJ
(3) Fe3O4 (s)  CO (g)  3 FeO (s)  CO2 (g)
H  19.0 kJ
These problems involve using heat of formation values that are found in the appendix F of your
textbook. Review of Sec. 7.4
(13) What is the enthalpy of the following reactions?
(a) SiF4(g) →
Si(s)
+ 2F2(g)
(b) SiF4(g) →
Si(g)
+ 2F2(g)
(c) SO3(g) + H2O(g)
→
(d) 3K2O2(s) + 3H2O(l)
H2SO4(aq)
→
6KOH(aq)
+ O3(g)
(e) Fe3O4(s) + 8HCl(g) → 2FeCl3(s) + FeCl2(s) + 4H2O(g)
(f)
Cl2 (g) + 2 HBr (g) → 2 HCl (g) + Br2 (g)
Answers:
1 answer = 249.8 kJ
2 answer = 235 kJ
3 answer = -18 kJ
4 answer = 72 kJ
5 answer = 204.0 kJ
6 answer = -83 kJ
7 answer = 886 kJ
8 answer = -46.2 kJ
9 answer = -230 kJ
10 answer = -705 kJ
11 Answer = -78 kJ
12 Answer = -976.03 kJ
13 a) (answer: +1615.0 kJ) b) (answer: +2065.0 kJ) c) (answer: -271.8 kJ) d) (answer: -412 kJ)
(not -411.7 kJ) e) (answer: -252 kJ) (not -251.6 kJ)