### Numerical problems based on normality equation

Problems
14. Commercially available concentrated hydrochloric acid contains 38% HCl by mass.
(a) What is the molarity of this solution? The density is 1.19 g/mL.
(b) What volume of concentrated HCl is required to make 1.00 L of 0.10 M HCl?
Solution
(a) 38% solution, means 38 g of HCl in 100 g of solution.
Then, Mass of the solution= 100 g

Molar mass of HCl = 36.5 g mol-1

(b) The molarity of conc. HCl sample = 12.38 mol/L
Molarity of HCl solution to be prepared = 0.10 mol/L
Volume of HCl solution to be prepared =1.00 L= 1000mL
Then, using molarity equation, M1V1 = M2V2

Thus, to obtain 1.0 L of 0.10 M HCl, one should dissolve 8.08 mL of concentrated HCl to make up the volume to 1.0L.
15. Concentrated nitric acid used as a laboratory reagent is usually 69% by mass of nitric acid. Calculate the volume of the solution which contained 23 g HNO3. Density of the concentrated HNO3 solution is 1.41 g cm-3.
Solution
Let, mass of conc. HNO3 sample = 100g
Mass of HNO3 in 100 g of sample = 69 g
Mass of water in 100 g of sample = 31 g
Density of conc. HNO3 sample = 1.41 g cm-3

= 70.92 cm3
Thus, 69 g of HNO3 is contained in 70.92 cm3 of conc. HNO3

Thus 23.6 cm3 concentrated HNO3 sample contained 23 g of HNO3.