Problem: At 63.5oC the vapor pressure of H2O is 175 torr, and that of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH.Assuming ideal-solution behavior, what is the vapor pressure of the solution at 63.5oC?

FREE Expert Solution

We are asked to use the colligative property of vapor pressure to determine the vapor pressure of the solution

We shall follow these steps in solving the problem:

Step 1: Determine the number of moles of ethanol and water.

Step 2: Determine the mole fraction of ethanol and water.

Step 3: Compute for the vapor pressure of the solution. The vapor pressure can be calculated as:


VP of solution = P°solvent χsolvent + P°solute χsolute 


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Problem Details

At 63.5oC the vapor pressure of H2O is 175 torr, and that of ethanol (C2H5OH) is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH.

Assuming ideal-solution behavior, what is the vapor pressure of the solution at 63.5oC?

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