Question

An aqueous KCl solution of density 1.20 g mL^-1 has a molality of 3.30 mol kg^-1. The molarity of the solution in mol L^-1 is ______. (Nearest integer)

Options

• 9

• 3

• 6

• 5

Answer 1

An aqueous KCl solution of density 1.20 g mL^-1 has a molality of 3.30 mol kg^-1. The molarity of the solution in mol L^-1 is 3.

Explanation:

Given, molality = 3.30 mol/kg

1 kg solvent = 3.3 mol KCl

= 3.3 mol × 74.5 g/mol

= 245.85 g

Weight of solution = Weight of solute + Weight of solvent

= 245.85 + 1000 g

= 1245.85 g

From density, d = `"m"/"V"`

or,  V = `"m"/"d"`

= `(1245.85 " g")/(1.20 " gL"^-1)`

= 1.0382 L

Molarity = `"Moles of solute"/"Volume of solution (in 1)"`

M = `(3.3 " mol")/(1038.21 xx 10^-3 " L")`

M = 3.17 ≈ 3