Write the answers in four decimal places. Box the final answer. Solve neatly.

5. In a hexane-octane solution containing 27.50 grams hexane and 42.5 grams of octane at 20C, the total pressure above the solution is 78.54 mmHg. At the same temperature, the vapor pressures of pure hexane and octane are 74.61 torr and 76.13 torr, respectively. Calculate (a) the activity coefficients of hexane and octane at this concentration and (b) the free energy of mixing to be expected for a corresponding ideal solution. (20PTS)