5. (16 pts) Ka=0.51 °C/m K-1.86 °C/m A student determines the molar mass of an unknown nonelectrolyte using its freezing

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5 16 Pts Ka 0 51 C M K 1 86 C M A Student Determines The Molar Mass Of An Unknown Nonelectrolyte Using Its Freezing 1 (47.03 KiB) Viewed 85 times

5. (16 pts) Ka=0.51 °C/m K-1.86 °C/m A student determines the molar mass of an unknown nonelectrolyte using its freezing point depression. She found that the equilibrium temperature of a mixture of ice and water was 0.5°C. When she added 14.7 g of the unknown to the mixture, the temperature fell to -4.5°C. She then poured off the solution through a screen into a beaker. The mass of the solution was 123.9 g. a. What is the molality of the unknown solution in water? b. What is the molar mass of the unknown? 6. (16 pts) A solution is made by dissolving 29.0 g of C17H₂1NO4 a nonvolatile nonelectrolyte, in 750.0 g water. The vapor pressure of pure water at 25 °C is 23.8 torr. a. Calculate the mole fraction of water, XH₂0 b. Calculate the vapor pressure of the C17H21NO4 solution at 25 °C.