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%.
Solution
We have given,
Mass percent of nitric acid in the sample =69%
Thus, 100g of nitric acid contains 69g of nitric acid by mass.
Molar mass of nitric acid contains 69g of nitric acid by mass.
Molar mass of nitric acid (HNO3)
=[1+14+3(16)]
=1+14+48
=63g mol-1
Therefore, number of moles in 69g of HNO3
= 69g/63g mol-1
=1.095 mol
Volume of 100g of nitric acid solution =
=Mass of solution/density of solution
= 100/1.41g ML-1
=70.92mL =70.92 x10-3L
Concentration of nitric acid
=1.095mole/70.92 mol L-1
Thus,
Concentration of nitric acid =15.44 mol/L
