Equilibrium Constant and Standard Free Energy Change
The equilibri...
Question
The equilibrium constant for the reaction given below is 2.0×10−7 at 300 K. Calculate the standard free energy change for the reaction. PCl5(g)⇌PCl3(g)+Cl2(g) Also, calculate the standard entropy change if, ΔH∘=28.40kJmol−1
A
38.48kJ,−33.6Jmol−1K−1
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B
48.48kJ,−33.6Jmol−1K−1
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C
38.48kJ,−43.6Jmol−1K−1
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D
48.48kJ,−43.6Jmol−1K−1
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Solution
The correct option is A38.48kJ,−33.6Jmol−1K−1 K=2.0×10−7T=300KΔH∘=28.4kJmol−1ΔG∘=−2.303RTlogK=−2.303×8314×10−3×300×log(2×10−7)=−5.744(log2−7)=−5.744(0.3010−7)=38.48kJ From ΔG∘=ΔH∘−TΔS∘⇒TΔS∘=ΔH∘−ΔG∘ΔS∘=ΔH∘−ΔG∘T=28.4−38.48300=−0.0336kJmol−1orΔS=−33.6Jmol−1K−1