For the reaction NH4Cl(S)→NH3(g)+HCl(g) at 250C, enthalpy change △=+177kJmol−1 and entropy change △S=+285JK−1mol−1. Calculate free energy change △G at 250C and product whether the reaction is spontaneous or not.
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Solution
Given, △H=177kJ/mol,△S=285JK−1mol−1,T=298K
Using the relation, △G=△H−T△S
△G=(177×103J/mol)−(298K)(285JK−1mol−1)
△G=92070J/mole
△G=92.07kJ/mole
△G>0
Since △G is positive, Hence reaction is non spontaneous.