Practice Questions I

Practice Questions I

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Using the following tabulated values of S° in the following table, calculate the value of S° for the reaction:
2CH3OH(g) + 3O2(g) 2CO2(g) + 4H2O(g).
Substance / S°(J/mol-K)
CH3OH(g) / 237.6
CH3OH(l) / 126.8
O2(g) / 205.0
CO2(g) / 213.6
H2O(g) / 188.8
H2O(l) / 69.9

a / 92.2 J/K
b / 313.9 J/K
c / -383.4 J/K
d
e / -40.2 J/K
313.9 J/K
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For each of the following processes, predict whether Ssys is positive or negative: (i) 2K(s) + Br2(l) 2KBr(s), (ii) 2MnO2(s) 2MnO(s) + O2(g)

a / (i) negative, (ii) positive
b / (i) positive, (ii) negative
c / (i) positive, (ii) positive
d / (i) negative, (ii) negative
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Which of the following processes are spontaneous and which are nonspontaneous: (i) separation of gaseous N2 and O2 molecules from each other, (ii) the reaction of sodium metal with chlorine gas to form sodium chloride, (iii) the dissolution of HCl(g) in water to form concentrated hydrochloric acid?

a / (i) nonspontaneous, (ii) spontaneous, (iii) spontaneous
b / (i) spontaneous, (ii) spontaneous, (iii) spontaneous
c / (i) spontaneous, (ii) spontaneous, (iii) nonspontaneous
d / (i) nonspontaneous, (ii) nonspontaneous, (iii) spontaneous
e / (i) spontaneous, (ii) nonspontaneous, (iii) spontaneous
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Maleic and fumaric acids are isomers of each other. What can be said about conversions between the two forms?

a / Maleic acid will spontaneously isomerize to fumaric acid at all temperatures.
b / Fumaric acid will spontaneously isomerize to maleic acid at all temperatures.
c. / Maleic acid will spontaneously isomerize to fumaric acid at high temperatures.
d. / Maleic acid will spontaneously isomerize to fumaric acid at low temperatures only.
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For which of the following reactions would you expect the entropy change to be closest to zero?

a / 2HgO(s) 2Hg(l) + O2(g)
b / N2(g) + O2(g) 2NO(g)
c / 2NO(g) + O2(g) 2NO2(g)
d / Zn(s) + 2H+(aq) Zn2+(aq) + H2(g)
e / 2H2(g) + O2(g) 2H2O(l)

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