Question

The free energy change accompanying a reaction is negative.
Which of the following options is the correct option?

• A. The reaction can occur spontaneously.
• B. The reaction can be used to do work by driving other reactions.
• C. The entropy must always be negative.
• D. Both $A$ and $B$

Answer 1

The correct option is D Both $A$ and $B$

For a chemical reaction to be spontaneous, it should have negative value of the Gibbs free energy change $\Delta G$.
$\Delta G=\Delta H-T\Delta S$
Consider following chemical reactions:
$A\to B$ , $\Delta G=+X$ ......(1)
$C\to D$, $\Delta G=-Y$ ...... (2)
If the magnitude of $\Delta G$ for second reaction is greater than the magnitude of $\Delta G$ for first reaction, $|Y|>|X|$, then if we add the reactions (1) and (2), the $\Delta G$ value for the coupled reaction will be negative. Due to this, the coupled reaction would be spontaneous.