The standard free energy change $(\Delta G' ^\circ)$ for ATP hydrolysis is $-30 kJ \cdot \text{mole}^{-1}$. The $\textit{in vivo}$ concentrations of ATP, ADP and $P_i$ in $E \textit{.coli}$ are $7.90, 1.04$ and $7.90$ mM, respectively. When $E\text{.coli}$ cells are cultured at $37 ^\circ C$, the free energy change $(\Delta G)$ for ATP hydrolysis $\textit{in viva}$ is _______ $kJ \cdot \text{mole}^{-1}$.