Question

A solution was prepared by dissolving 29.0g KCl in 225 g of water.

1) Calculate the mass percent of KCl in the solution.

2)Calculate the mole fraction of the ionic species KCl in the solution.

3) Calculate the molarity of KCl in the solution if the total volume of the solution is 239 mL.

4) Calculate the molarity of KCl in the solution.

Answer 1

1)
mass % = mass of KCl * 100 / total mass
                 = (29*100) / (29+225)
                 = 11.4 %

2)
moles of KCl = mass / molar mass
                          = 29/74.55
                          = 0.389 mol

moles of water = mass / molar mass
                                =225/18
                                = 12.5 mol

mole fraction of K+ = mole fraction of Cl-
                          = moles of KCl / total moles
                          =0.389 / (0.389 + 12.5)
                          = 0.03

3)
Molarity = number of moles of KCl / volume of solution in L
                   = 0.389 / 0.239
                   = 1.63

4)
Molality = number of moles of KCl / mass of solvent in Kg
                   = 0.389 / 0.225
                   = 1.73