Question

Identify the correct statement for change of Gibbs energy for a system ($\Delta$G${}_{system}$) at constant temperature and pressure:

• A. If $\Delta$G${}_{system}$ > 0, the process is spontaneous
• B. If $\Delta$G${}_{system}$ = 0, the system has attained equilibrium
• C. If $\Delta$G${}_{system}$ = 0, the system is still moving in a particular direction
• D. If $\Delta$G${}_{system}$ < 0, the process is not spontaneous

Answer 1

The correct option is B If $\Delta$G${}_{system}$ = 0, the system has attained equilibrium

At equilibrium, the entropy of system is maximum. Therefore change in entropy i.e; $△S=0$

Process	Sign of $△S$	Sign of $△G$
Spontaneous	Positive, $△S_{total}>0$	Negative, $△G<0$
Non-Spontaneous	Negative, $△S_{total}<0$	Positive, $△G>0$
Equilibrium	$△S_{total}=0$	$△G=0$