Calculate the mass fraction of nitric acid if it is known that the acid contained in 200 g

Calculate the mass fraction of nitric acid if it is known that the acid contained in 200 g of this solution has completely reacted with 4 g of sodium hydroxide.

1. Let’s compose the equation of the proceeding chemical reaction.

HNO3 + NaOH = NaNO3 + H2O.

2. Find the amount of reacted sodium hydroxide.

n (NaOH) = m (NaOH) / M (NaOH) = 4 g / 40 g / mol = 0.1 mol.

3. According to the reaction equation, we find the amount of nitric acid and, as a result, its mass fraction in the solution.

n (HNO3) = n (NaOH) = 0.1 mol.

m (HNO3) = n (HNO3) * M (HNO3) = 0.1 mol * 63 g / mol = 6.3 g.

ω (HNO3) = m (HNO3) / m (solution) * 100% = 6.3 g / 200 g * 100% = 3.15%.

Answer: ω (HNO3) = 3.15%.