As we saw in Chapter $18,$ the free energy $(\Delta G)$ of a reaction is related to the cell potential by the equation $\Delta G=-n F E .$ In Figure $P 21.5,$ two solutions of $\mathrm{Na}^{+}$ of different concentrations are separated by a semipermeable membrane. Calculate $\Delta G$ for the transport of $\mathrm{Na}^{+}$ from the side with higher concentration to the side with lower concentration. (Hint: See Problem 21.45.) (FIGURE CAN'T COPY)