Ap Chemistry Worksheet - Dr. Kathleen Gorski, Wilbraham And Monson Acaddemy Page 11
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245.65 From the enthalpies of reaction
(g) ! 2 HF(g) ΔH = -537 kJ
H
(g) + F
2
2
C(s) + 2 F
(g) ! CF
(g)
ΔH = -680 kJ
2
4
2 C(s) + 2 H
(g) ! C
H
(g)
ΔH = +52.3 kJ
2
2
4
calculate for the reaction of ethylene with F
:
2
C
H
(g) + 6 F
(g) ! 2 CF
(g) + 4 HF (g)
2
4
2
4
5.74 Using values from Appendix C, calculate the value of ΔH° for each of the following
reactions:
(a) CaO (s) 2 HCl (g) ! CaCl
(s) + H
O (g)
2
2
(b) 4 FeO (s) + O2 (g) ! 2 Fe
O
(s)
2
3
(c) 2 CuO (s) + NO (g) ! Cu
O (s) + NO
(g)
2
2
(d) 4 NH
(g) + O
(g) ! 2 N
H
(g) + 2 H
O (l)
3
2
2
4
2
5.86 The heat of combustion of ethanol, C
H
OH (l), is -1367 kJ/mol. A batch of Sauvignon Blanc
2
5
wine contains 10.6% ethanol by mass. Assuming the density of the wine to be 1.0 g/mL, what is
the caloric content due to the alcohol (ethanol) in a 6-oz glass of wine (177 mL)?
5.104 (a) Calculate the standard enthalpy of formation of gaseous diborane (B
H
) using the
2
6
following thermochemical information:
4 B (s) + 3 O
(g) ! 2 B
O
(s)
ΔH° = -2509.1 kJ
2
2
3
2 H
(g) + O
(g) ! 2 H
O (l)
ΔH° = -571.7 kJ
2
2
2
B
H
(g) + 3 O
(g) ! B
O
(s) + 3 H
O (l)
ΔH° = -2147.5 kJ
2
6
2
2
3
2
(b) Pentaborane (B
H
) is another boron hydride. What experiment or experiments would you
5
9
need to perform to yield the data necessary to calculate the heat of formation of B
H
(l)?
5
9
Explain by writing out and summing any applicable chemical reactions.
5.110 The Sun supplies about 1.0 kilowatt of energy for each square meter of surface area (1.0
2
kW/m
, where a watt = 1 J/s). Plants produce the equivalent of about 0.20 g of sucrose
(C
H
O
) per hour per square meter. Assuming that the sucrose is produced as follows,
12
22
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calculate the percentage of sunlight used to produce sucrose.
12 CO
(g) + 11 H
O (l) ! C
H
O
+ 12 O
(g)
ΔH° = 5645 kJ
2
2
12
22
11
2
[5.111] It is estimated that the net amount of carbon dioxide fixed by photosynthesis on the
16
landmass of Earth is 5.5 x 10
g/yr of CO
. Assume that all this carbon is converted into
2
glucose. (a) Calculate the energy stored by photosynthesis on land per year in kJ. (b) Calculate
the average rate of conversion of solar energy into plant energy in MW (1 W = 1 J/s). A large
3
nuclear power plant produces about 10
MW. The energy of how many such nuclear power
plants is equivalent to the solar energy conversion?
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