Calculate the mass fraction (%) of nitric acid in the solution if it is known that 200 g of this solution

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

Given:
m solution (HNO3) = 200 g
m (NaOH) = 4 g

Find:
ω (HNO3) -?

Solution:
1) HNO3 + NaOH => NaNO3 + H2O;
2) n (NaOH) = m / M = 4/40 = 0.1 mol;
3) n (HNO3) = n (NaOH) = 0.1 mol;
4) m (HNO3) = n * M = 0.1 * 63 = 6.3 mol;
5) ω (HNO3) = m * 100% / m solution = 6.3 * 100% / 200 = 3.15%.

Answer: Answer: Mass fraction of HNO3 is 3.15%.