Part A If 0.900 of a nonvolatile nonelectrolyte are dissolved in 3.30 mol of wat
ID: 767599 • Letter: P
Question
Part A If 0.900 of a nonvolatile nonelectrolyte are dissolved in 3.30 mol of water, what is the vapor pressure PH2O of the resulting solution? The vapor pressure of pure water is 23.8 torr at 25deg C . Express your answer with the appropriate units. Solutions containing volatile solutes In solutions composed of two liquids ( and ), each liquid contributes to the total vapor pressure above the solution. The total vapor pressure is the sum of the partial pressures of the components: where and are the vapor pressures of pure and , respectively. Part B A solution is composed of 1.90 mol cyclohexane (Pcy=97.6 torr) and 2.90 mol acetone (Pac=229.5 torr). What is the total vapor pressure Ptotal, above this solution? Express your answer with the appropriate units.Explanation / Answer
1. P = P0 a x Xa where P0 is the vapor pressure of pure a and Xa is the mole fraction of a. mole fraction a = moles a / total moles = 3.30 / (3.30 + 0.280) = 0.922 P = (23.8 torr)(0.922) = 21.9 torr 2. P total = (P0 a x Xa) + (P0 b x Xb) mole fraction cyclohexane = (1.20) / (1.20 + 2.50) = 0.324 mole fraction acetone = 1 - 0.324 = 0.676 P total = (97.6 torr)(0.324) + (229.5 torr)(0.676) = 187 torr