Q. 19. For the reaction

2Ag+Bg2DgUθ=-10.5kJandSθ=-44.1JK-1

Calculate Gθfor the reaction, and predict whether the reaction may occur spontaneously.

NEETprep Answer:
For the given reaction,
2Ag+Bg2Dgng=2-3=-1mole
Substituting the value of Uθ in the expression of H
Hθ=Uθ+ngRT
=-10.5kJ--18.314×10-3kJK-1mol-1298K=-10.5kJ-2.48kJHθ=-12.98kJ

Substituting the values of Hθ and Sθ in the expression of Gθ:
Gθ=Hθ-TSθ

=-12.98kJ--298K-44.1JK-1=-12.98kJ+13.14kJGθ=+0.16kJ

Since Gθ for the reaction is positive, the reaction will not occur spontaneously.