1.In which reaction is S° expected to be positive? A. H2O(l) + 2SO2(g) H2SO4(l)
ID: 968877 • Letter: 1
Question
1.In which reaction is S° expected to be positive?
A. H2O(l) + 2SO2(g) H2SO4(l)
B. 2C2H6(g) + 7O2(g) 4CO2(g) + 6H2O(l)
C. Ga(l) Ga(s)
D. CO2(g) CO2(s)
E. none of these choices are correct.
2.Assuming H and S are constant with respect to temperature, under what conditions will a chemical reaction be nonspontaneous at all temperatures?
A. H is positive, and S is negative.
B. H is negative, and S is positive.
C. S = 0, and H is positive.
D. H = 0, and S is negative.
E. None of these choices are correct.
Water gas, a commercial fuel, is made by the reaction of hot coke carbon with steam:
When equilibrium is established at 797°C, the concentrations of CO, H2, and H2O are 4.00 × 10–2, 4.00 × 10–2, and 1.00 × 10–2 mol/L, respectively. Calculate the value of G° for this reaction at 797°C.
A. 16.3 kJ
B. 12.1 kJ
C. -12.3 kJ
D. 53.3 kJ
E. None of these choices are correct.
Explanation / Answer
1) C. Ga(l) Ga(s) , for this reaction only S° expected to be positive. As, the entropy is measure of randomness of the system which increases on increasing the more amount of gaseous products.
2) A. H is positive, and S is negative.
C. S = 0, and H is positive.
D. H = 0, and S is negative.
3) C + H2O <----> CO + H2
Keq = 0.04*0.04/0.01
= 0.16
G° = -RTlnKeq
= - 2.303*0.008314*1070*log(0.16)
= 16.3 KJ
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