Asolution of sodium chloride in water has a vapor pressure of 17.5 torr at 25°c. what is the mole fraction of nacl solute particles in this solution? what would be the vapor pressure of this solution at 45°c? the vapor pressure of pure water is 23.8 torr at 25°c and 71.9 torr at 45°c and assume sodium chloride exists as na⁺ and cl⁻ ions in solution.

Explanation:

Since, NaCl exists as and in solution. Therefore, Van't Hoff factor (i) will be equal to 2.

Now, we assume that there are "n" moles of NaCl in the given solution. And, we assume that there is 1 kg of solvent (water).

So,

            0.264 =

               n = 0.132

Also, moles of water will be calculated as follows.

            Moles of water =

                                      = 55.56 mol

Hence, mole fraction of NaCl is calculated as follows.

         Mole fraction =

                                =

Hence, mole fraction of NaCl will be .

At , the vapor pressure will be calculated as follows.

              71.9 - p = 18.98

                      p = 52.92 torr

Therefore, vapor pressure of the given solution is 52.92 torr.

it should be p1 v1 = p2 v2