E. coli cultivated at $298 \mathrm{~K}$ uptakes an uncharged compound (A) by passive diffusion. The intracellular and extracellular concentrations of $\mathrm{A}$ are $0.001 \mathrm{M}$ and $0.1 \mathrm{M}$, respectively. If the value of the ideal gas constant $\mathrm{R}$ is $1.9872 \text { cal.mol }^{-1}$. $\mathrm{K}^{-1}$, the free-energy change (in $\mathrm{kcal.mol}^{-1}$) for this passive diffusion of $\mathrm{A}$ (rounded off to two decimal places) is ______________.