questions

Section 19.5

1. Calculate ∆, So for the following reaction at 25oC;

N2(g) + 2 O2(g) 2 NO2(g)

(a) -480.1 J/K ∙ mol-rxn

(b) -121.6 J/K ∙ mol-rxn

(c) 121.6 J/K ∙ mol-rxn

(d) 480.1 J/K ∙ mol-rxn

Answer: (b) -121.6 J/K ∙ mol-rxn

2. Calculate ∆, So (universe) for the following reaction at 25.0 oC:

C (graphite) + O2 (g) CO2 (g)

(a) -1317 J/K ∙ mol-rxn

(b) 3.1 J/K ∙ mol-rxn

(c) 4.4 J/K ∙ mol-rxn

(d) 1320 J/K ∙ mol-rxn

Answer: (d) 1320 J/K ∙ mol-rxn

3. If ∆,Ho= + 467.9 kj/mol-rxn and ∆, So = +560.7 j/k ∙ mol-rxn for the following reaction

2 Fe2O3(s) + 3 C (graphite) 4Fe(s) + 3 CO2(g)

Then, under standard conditions, this reaction will be spontaneous

(a) at all temperatures

(b) at higher temperatures

(c) at lower temperatures

(d) at no temperatures

Answer: (b) at higher temperatures