NCERT Class XI Chemistry Thermodynamics Solutions

Question : 17

Total: 22

For the reaction at 298 K, 2A + B → C, ΔH = 400 kJmol–1 and ΔS = 0.2 kJK–1mol–1. At what temperature will the reaction become spontaneous considering ΔH and ΔS to be constant over the temperature range.

Solution:

According to Gibbs Helmholtz equation, ΔG = ΔH – TΔS.
At equilibrium, ΔG = 0
∴ T =

ΔH

ΔS

400

0.2

4000

= 2000 K
Thus, the reaction will be spontaneous at temperature above 2000 K.
[Since Above 2000 K, ΔG = –ve]

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