Question

Find the molarity and molality of 37.0 wt % HCl. The density of the reagent is 1.19 g/mL.

Answer 1

Solution for molality:

1) Let us assume 100.0 grams of solution. Therefore:

37 g is HCl
63 g is H₂O

2) Calculate the molality:

moles HCl = 37 g / 36.5 g/mol = 1.014 mol
kg of water = 0.063 kg

molality = 1.014 mol / 0.063 kg = 16.09 molal

Solution for molarity:

1) Determine moles of HCl in 100.0 g of 37% solution:

37 g of this solution is HCl

37 g / 36.5 g/mol = 1.014 mol

2) Determine volume of 100.0 g of solution:

density = mass / volume

1.19 g/mL = 100.0 g / x

x = 84.03 mL

3) Determine molarity:

1.014 mol / 0.084 L = 12.07 M