Name ______Mr. Perfect__________________________________ Date ________Sp 17___________
1. The chemistry of nitrogen oxides is very versatile. Consider the following reactions:
NO(g) + NO2(g) → N2O3(g)
NO(g) + NO2(g) + O2(g) → N2O5(g)
2NO2(g) → N2O4(g)
2NO(g) + O2(g) → 2NO2(g)
N2O5(s) → N2O5(g)
ΔH°rxn = -39.8 kJ
ΔH°rxn = -112.5 kJ
ΔH°rxn = -57.2 kJ
ΔH°rxn = -114.2 kJ
ΔH°sub = +54.1 kJ
Calculate the heat of reaction for the following reaction and clearly state if the system is
exothermic or endothermic: (4 pts)
N2O3(g) + N2O5(s) → 2N2O4(g)
Apply Hess’s Law:
N2O3(g) → NO(g) + NO2(g)
N2O5(g) → NO(g) + NO2(g) + O2(g)
4NO2(g) → 2N2O4(g)
2NO(g) + O2(g) → 2NO2(g)
N2O5(s) → N2O5(g)
_____________________________
+39.8 kJ
+112.5 kJ
-114.4 kJ
-114.2 kJ
+54 kJ
__________
N2O3(g) + N2O5(s) → 2N2O4(g)
-22.2 kJ = ΔH°rxn
The system is exothermic thus heat is released into the surroundings.
Chemistry 101 Quiz 4 (Take Home)
Due at the 4/11/17 course lecture.
Name ______Mr. Perfect__________________________________ Date ________Sp 17___________
2. Kerosene is used as rocket fuel in a highly refined form known as RP-1 and is often burned
with liquid oxygen. The combustion of kerosene, C12H26, with oxygen in the gas phase has a
ΔH°rxn equal to -7513 kJ.
(a) Calculate the heat produced by the combustion of 0.5 gallons of kerosene. (3 pts)
Balanced Equation:
2C12H26 + 37O2 → 24CO2 + 26H2O
0.50 𝑔 𝑔𝑎𝑙 ×
ΔH°rxn = -7513 kJ
3.79 𝐿 1000 𝑚𝐿 0.749 𝑔
𝑚𝑜𝑙
−7513 𝑘𝐽
×
×
×
×
= −𝟑𝟏𝟑𝟔𝟒 𝒌𝑱
1 𝑔𝑎𝑙
1𝐿
𝑚𝐿
170 𝑔 2 𝑚𝑜𝑙 𝐶12 𝐻26
(b) How many gallons of kerosene must be burned to produce 1250 British Thermal Units of
energy? (2 pts)
−1250 𝐵𝑡𝑢 ×
1.055 𝑘𝐽
1 𝑔𝑎𝑙
×
= 𝟎. 𝟎𝟐𝟏 𝒈𝒂𝒍
1 𝐵𝑡𝑢
−62728 𝑘𝐽
Chemistry 101 Quiz 4 (Take Home)
Due at the 4/11/17 course lecture.