$G$ denotes the Gibbs free energy of a binary mixture, $n_{T}$ denotes the total number of moles present in the system, $\mu _{i}$ is the chemical potential of the $i^{th}$ component $\left ( \mu _{i} \neq 0\:and \:\mu _{1}> \mu _{2}\right )$ and $x_{i}$ is the mole fraction of the $i^{th}$ component. The correct variation of $G/n_{T}$ (in $J$/mol) at constant temperature and pressure is given by