Question

Which is correct about $\Delta G$?
A.$\Delta G = \Delta H - T\Delta S$
B.At equilibrium $\Delta {G^ \circ } = 0$
C.At eq. $\Delta G = - RT\log K$
D.$\Delta G = \Delta {G^ \circ } + RT\log K$

Answer 1

Hint: This question gives the knowledge about Gibbs free energy. $\Delta G$ is positive, the reaction becomes non- spontaneous, when $\Delta G$ is negative the reaction becomes spontaneous and when $\Delta G$ has zero value this means the reaction is taking place at equilibrium.

Complete step by step answer:
Gibbs free energy is defined as the energy which is useful in determining the maximum amount of reversible work done by a thermodynamic system at constant pressure and temperature. Gibbs free energy is a thermodynamic potential. The symbol used for Gibbs free energy is $G$.
The Gibbs free energy equation is designated as follows:
$\Delta G = \Delta H - T\Delta S$
Where $G$ is Gibbs free energy, $H$ is enthalpy, $T$ is temperature and $S$ is entropy. This equation is also known as Gibbs Helmholtz equation.
Gibbs free energy does not depend upon the path because it is a state function and state function does not depend upon path. Gibbs free energy generally determines the extent and direction of chemical change. Gibbs free energy is applicable only for those reactions in which pressure and temperature remains constant. $\Delta G$ helps in determining whether the reaction is thermodynamically possible or not.
$\Delta G$ is positive, the reaction becomes non- spontaneous, when $\Delta G$ is negative the reaction becomes spontaneous and when $\Delta G$ has zero value this means the reaction is taking place at equilibrium. When $\Delta G$ is negative, the reaction occurs spontaneously and this process is known as exergonic.

Therefore, option A is the correct option.

Note: Always remember that $\Delta G$ is positive, the reaction becomes non- spontaneous, when $\Delta G$ is negative the reaction becomes spontaneous and when $\Delta G$ has zero value this means the reaction is taking place at equilibrium.