Which quantity out of rG and rG will be zero at equilibrium?


Gibbs energy for a reaction in which all reactants and products are in standard state. rG is related to the equilibrium constant of the reaction as follows
rG=rG+RTInK
At equilibrium, 0=rG+RTInK(rG=0)
or rG=-RTInK
rG=0 when K=1
For all other values of K. rG will be non-zero.