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3. In a hexane-octane solution containing 27 50 grams hexane and 425 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)