Tamil Nadu Board of Secondary EducationHSC Science Class 11th

For the reaction AgX2OX(s)⟶2AgX(s)+12OX2X(g): ΔH = 30.56 kJ mol−1 and ΔS = 6.66 JK−1 mol−1 (at 1 atm). Calculate the temperature at which ΔG is equal to zero. Also predict the direction - Chemistry

Numerical

For the reaction $\ce{Ag2O_{(s)} -> 2Ag_{(s)} + 1/2O2_{(g)}}$: ΔH = 30.56 kJ mol−1 and ΔS = 6.66 JK−1 mol−1 (at 1 atm). Calculate the temperature at which ΔG is equal to zero. Also predict the direction of the reaction

1. at this temperature and
2. below this temperature.

Solution

Given, ∆H = 30.56 kJ mol−1 = 30560 J mol−1

∆S = 6.66 × 103 kJ K1 mol1

T = ?

at which ∆G = 0

∆G = ∆H – T∆S

0 = ∆H – T∆S

T = (Δ"H")/(Δ"S")

T = (30.56  "kJ mol"^-1)/(6.66  xx 10^-3  "kJ mol"^-1)

T = 4589 K

1. At 4589K; ∆G = 0 the reaction is in equilibrium.
2. at temperature below 4598 K; ∆H > T∆S
∆G = ∆H – T∆S > 0, the reaction in the forward direction, is non spontaneous. In other words the reaction occurs in the backward direction.
Concept: Gibbs Free Energy (G)
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Tamil Nadu Board Samacheer Kalvi Class 11th Chemistry Volume 1 and 2 Answers Guide
Chapter 7 Thermodynamics
Evaluation | Q II. 35. | Page 226
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