ΔH and ΔS for the reaction, Ag2O(s)⟶2Ag(s)+12O2(g) are 30.56kJmol−1 and 66.0JK−1mol−1 respectively. Calculate the temperature at which free energy change for the reaction will be zero. Predict whether the forward reaction will be forward above or below this temperature.
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Solution
We know that ΔG=ΔH−TΔS At equilibrium ΔG=0 so that 0=ΔH−TΔS or T=ΔHΔS Given that, ΔH=30.56kJmol−1=30560Jmol−1 ΔS=66.0JK−1mol−1 T=3056066=463K Above this temperature, ΔG will be negative and the process will be spontaneous in forward direction.