NS102-200901-ProblemSet5

NS102-200901-ProblemSet5 - NS102 Study Problems Set 5 The...

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NS102 Study Problems Set 5 The set contains study problems and exam questions from the previous semesters on spontaneity, Gibbs energy and chemical equilibrium. The gas constant (R) = 8.314 J mol -1 K -1 = 0.082 atm L mol -1 K -1 1. An important reaction in the production of sulfuric acid is the oxidation of SO 2 (g) to SO 3 (g). 2 2 3 2SO (g) O (g) 2SO (g)  At 298 K, ΔG 141.6 kJ, ΔH 198.4 kJ and ΔS 187.9J/K       a) Is this reaction spontaneous at 25 °C? Predict how G will change with increasing temperature. b) What might be the reason for ΔShaving a negative value? c) Assuming H and S are constant with increasing T, is the reaction spontaneous at 900 °C? d) Find the temperature (°C) at which the spontaneity trend changes from spontaneous to non-spontaneous for this reaction Answer : (a) Reaction is spontaneous at 298 K. G will become less negative (less spontaneous) with increasing T; (b) 3 mol of gas molecules 2 mol of gas molecule. Therefore order increases and entropy decreases; (c) G=22.0 kJ at 900°C, Reaction is non- spontaneous; (d) T=783° 2.
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NS102-200901-ProblemSet5 - NS102 Study Problems Set 5 The...

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