Question

An aqueous solution contains 5.8% KBr by mass.

Calculate the molality of the solution.

Calculate mole fraction of the solution.

Please help

Answer 1

Given An aqueous solution contains 5.8% KBr by mass.

That means 5.8 g of KBr present in 100 mL(=0.1 L) of the solution

Molar mass of KBr = At.mass of K + At.mass of Br

                               = 39 + 80

                               = 119 g/mol

So number of moles of KBr , n = mass/molar mass

                                                 = 5.8 g / 119 (g/mol)

                                                 = 0.0487 mol

(a) Molarity , M = number of moles / Volume in L

                    = 0.0487 mol / 0.1 L

                    = 0.487 M

We cannot calculate the mole fraction of solution we calculate only the mole fraction of either solute or solvent