Calculate the concentration of nitric acid in moles per litre in a sample which has a density, 1.41 g mL–1 and the mass per cent of nitric acid in it being 69%.

Q-6 Calculate the concentration of nitric acid in moles per litre in a sample which has a density, 1.41 g mL–1 and the mass per cent of nitric acid in it being 69%.

Answer
Mass percent of nitric acid in the sample = 69 % [Given]
Thus, 100 g of nitric acid contains 69 g of nitric acid by mass.
Molar mass of nitric acid (HNO3)
                                                  = {1 + 14 + 3(16)} g mol–1
                                                  = 1 + 14 + 48
                                                  = 63 g mol–1
∴ Number of moles in 69 g of HNO3
                                               
Volume of 100g of nitric acid solution
                                           
Concentration of nitric acid
                                           
∴Concentration of nitric acid = 15.44 mol/L(answer)