Chemistry (Chang), 10th Edition

Chapter 18: Entropy, Free Energy, and Equilibrium

Self Assessment B

1
Which of the following reactions shows the greatest increase in entropy?
A)SO3(g) -----> 2 SO2(g) + O2(g)
B)H2O(l) ----> H2O(s)
C)Br2(l) ----> Br2(g)
D)H2O2(l) ----> H2O(l) + 1/2 O2(g)
2
Without consulting entropy tables, predict the sign of DS for the following process and choose the correct reasoning for your prediction: N2(g, 10 atm) ----> N2(g, 1 atm). The mass of N2 remains constant.
A)positive; there is an increase in the number of gas molecules.
B)positive; the gas expands into a larger volume.
C)negative; the gas is compressed into a smaller volume.
D)negative; the gas expands into a larger volume.
E)negative; there is a decrease in the number of gas molecules.
3
Which of the following reactions will have the most positive DHo?
A)N2(g) ----> 2 N(g)
B)F2(g) ----> 2 F(g)
C)O2(g) ----> 2 O(g)
D)These reactions would all have the same DHo.
4
Rubidium has a heat of vaporization of 69.0 kJ/mol and an entropy of vaporization of 71.9 J/K.mol. Calculate the boiling point of rubidium.
A)687 K
B)273 K
C)32 oF
D)687 oC
5
Calculate DSorxn for the following reaction:

4 Cr(s) + 3 O2(g) ----> 2 Cr2O3(s).
SubstanceDSo, J/K·mol
Cr(s)23.77
O2(g)205.138
Cr2O3(s)81.2
A)548.1 J/K
B)147.7 J/K
C)-147.7 J/K
D)-548.1 J/K
6
For the process C6H6(l) ----> C6H6(s) at a temperature above the freezing point of C6H6,
A)DS is positive.
B)DH is positive.
C)DG is positive.
D)DG = O.
7
Keq = 7.0 at 35 oC for the reaction A + B ----> C + Calculate DGo for this reaction.
A)- 4.98 kJ
B)2.46 kJ
C)- 5.66 kJ
D)4983 kJ
8
Sodium carbonate can be prepared by heating sodium bicarbonate.

2 NaHCO3(s) ----> Na2CO3(s) + CO2(g) + H2O(g).

Given that DHo = 128.9 kJ and DSo = 321 J/K·mol for this reaction, at what temperature will K = 1?
A)401.6 K
B)401.6 oC
C)33.1 K
D)33.1
9
Consider the reaction SO2(g) + NO2(g) ----> SO 3(g) + NO(g), which occurs at 298 K. Given the information below, determine which of the following choices is correct.
compoundDGo, kJ/mol
SO2(g)-300.4
SO3(g)-370.4
NO(g)86.7
NO2 51.8
A)K > 1; DG > 0
B)K > 1; DG < 0
C)K < 0; DG > 0
D)K < 0; DG < 0
10
In the following reaction, SO2(g) + CuO(s) ----> Cu(s) + SO3(g), sulfur dioxide _____ reduce copper(II) oxide at 298 K.
substanceDHof, (kJ/mol)So, J/K·mol
SO2(g)-296.2248.5
CuO(s)-157.342.7
Cu(s)033.5
SO3(g)-395.4256.1
A)will; DGo is positive.
B)will; DGo is negative.
C)will not; DGo is positive.
D)will not; DGo is negative.
E)will not; DGo = 0.
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