Question

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 1

Mass percent of 69% means tat 100g of nitric acid solution contain 69 g of nitric acid by mass. 

Molar mass of nitric acid (HNO₃) = 1+14+48 = 63g mol^-1 

Number of moles in 69 g of HNO₃ = 69/63 moles = 1.095 moles 

Volume of 100g nitric acid solution = 100/1.41 mL = 70.92 mL = 0.07092 L 

∴ Conc. of HNO₃ in moles per litre = 1.095/0.07092 = 15.44 M