Download Homework 11 Solutions

Chemistry 201
Assignment 11
Name _______________________________
Note: pay close attention to G versus Go
Indicate whether each of the following must always, can sometimes, or cannot ever be true for a
spontaneous endothermic process and an extensive exothermic process.
spontaneous endothermic
extensive exothermic
H>0
must be true
can be true
1a
cannot be true
Go < 0
must be true
must be true
can be true
1c
must be true
can be true
1e
must be true
can be true
1g
must be true
can be true
1i
1d
must be true
can be true
1f
must be true
can be true
1h
must be true
can be true
1j
can be true
1l
cannot be true
can be true
1k
cannot be true
2. Consider the reaction
Al2O3(s) + 3C(graphite) + 3Cl2(g)
can be true
cannot be true
cannot be true
Euniv < 0
must be true
cannot be true
cannot be true
S>0
1b
cannot be true
cannot be true
G<0
can be true
cannot be true
cannot be true
Suniv = 0
must be true
must be true
cannot be true
2AlCl3(s) + 3CO(g)
Using the values in Appendix B, or the Thermodynamic Properties Resource in the on-line
textbook, determine the following at 298 K:
Ho = ________________ kJ/mol Answer: -39.54 kJ/mol
So = ________________ J/mol-K Answer: 241 J/mol-K
Go = _________________kJ/mol Answer: -111.6 kJ/mol
What is K at 298K?
Answer: 3.73e+19
Assume that Ho and So are temperature independent to determine the following at 950 K.
(Hint: use your values of Ho and So above to calculate Go at the new temperature.)
Go = _____________ kJ/mol Answer: -268.49 kJ/mol
K = _______________ Answer: 5.89e+14
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3. Consider the following reaction:
N2(g) + 3H2(g) 2NH3
K = 6.09e+05 at 25 oC(g)
Report all answers to three significant figures!
a) Determine the reaction quotient when the partial pressures of the gases are the following.
N2 = 6.60 atm; H2 = 14.10 atm; NH3 = 3.40 atm
Q = __________. Answer: 1.3e-03
b) Determine the value of G when the reaction mixture is the one described in Part a.
G = _____________ kJ Answer: -4.94e+01
4. Consider the following reaction at 298 K :
NH41+ + CN1- HCN + NH3
Determine Go, Q, and G at 298K for the following concentrations if K = 1.70
[NH3]
[NH41+]
[CN1-]
[HCN]
0.190 M
0.160 M
0.120 M
0.190 M
a.
Go = ___________ kJ/mol. Answer: 1.307 kJ/mol
b. Q = _____________. Answer: 0.844
c.
G = ____________ kJ/mol. Answer: 0.887 kJ/mol
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