Asolution is prepared by dissolving 23.7 g of cacl2 in 375 g of water. the density of the resulting solution is 1.05 g/ml. the mole fraction of cl- in this solution is

The density of the solution =1.05 g/ml.
The total mass of the resulting solution is = 398.7 g (CaCl2 + water)

Find moles of CaCl2 and water.
Molar mass of CaCl2 = 110 (approx.)

Moles of CaCl2 = 23.7 / 110  = 0.22
so, moles of Cl- ion = 2 x 0.22 = 0.44  (because each molecule of CaCl2 will give two Cl- ions)
Moles of water = 375 / 18 = 20.83

Now, Mole fraction of CaCl2 =  (moles of CaCl2) / (total moles)

total moles = moles of Cl- ions + moles of Ca2+ ions + moles of water

                  = 0.44 + 0.22 + 20.83

=21.49

So, mole fraction = 0.44 / (21.49) = 0.02

Guess what !!! density is not used. No need