The vapor pressure of pure acetone is 266 torr. when a non-volatile solute is added, the vapor pressure of acetone above the solution falls to 214 torr. what is the mole fraction of the non-volatile solute in the solution?

Answer : The mole fraction of the non-volatile solute in the solution is 0.195

Explanation :

According to the relative lowering of vapor pressure, the vapor pressure of a component at a given temperature is equal to the mole fraction of that component of the solution multiplied by the vapor pressure of that component in the pure state.

Formula used :

where,

= vapor pressure of the pure solvent (acetone)  = 266 torr

= vapor pressure of the solution = 214 torr

= mole fraction of solute  = ?

Now put all the given values in the above formula, we get:

Therefore, the mole fraction of the non-volatile solute in the solution is 0.195