Question

For the reversible reaction $A_{(s)}+B_{(g)} \rightleftharpoons C_{(g)}+D_{(g)}: \Delta G^{0}=-350 kJ .$ Which one of the following statements is true?

• A. Equilibrium constant is greater than one
• B. The entropy change is negative.
• C. The reaction is thermodynamically not feasible
• D. The reaction should be instantaneous

Answer 1

Answer: (A)

Equilibrium constant is greater than one

Answer 2

In the reversible reaction,

$A(s)+B(g) \rightleftharpoons C(g)+D(g);$
$\Delta G^{\circ}=-350\, k J$

Since, the randomness increases (because solid is changing into gas), entropy will increase and thus, $\Delta S$ is positive. Reversible reaction never undergo to completion (ie, never be instantaneous).

$\because$ For the given reaction, $\Delta G^{\circ}=-350\, kJ$ and we know that

$\Delta G^{\circ} =-R T \log K$
$-350 =-R T \log K$

ie, $K$ (equilibrium constant) is greater than one.

Moreover, the reaction is thermodynamically feasible.