Question

7. (8%) How to dispense one liter of 3 M HCl solution if you have a bottle of HCl that you find in the chemical stores? The bottle contains the following information: “37% w / w HCl (aq), density: 1.19 kg / L, molecular weight of HCl = 36.5 g / mol. ”

Answer 1

Given, density of concentrated solution = 1.19 kg/L = 1190 g/L  

37 % w/w means we have 36.5 g per 100 g of solution

molecular weight is given as 36.5 g/mol.

Concentration can be found out using the formula,

concentration(M) =purity x density x molecular weight

=> concentration(M) = (36.5 g/100 g solution) x 1190 g/L x ( 1 mol HCl/36.5 g)

=> concentration(M) = 11.9 mol/L = 11.9 M

This implies that the solution has the molarity of 11.9 M.

Now,

C₁ = concentration of the concentrated solution (11.9 M)

V₁= volume needed to prepare the diluted solution ( say X)

C₂= concentration of the diluted solution (3M given )

V₂= total volume of solution = 1 L = 1000 mL

Again,

C₁V₁ = C₂V₂

=>11.9 M * X = 3 M x 1000 mL

=> X = 252.1 mL

Hence, in order to prepare 1000 mL of a solution of HCl to 3M you have to take 252.1 mL of the concentrated solution and add 747.9 mL distilled water to make up the total volume to 1000 mL (1L).