58. Solving a chemistry problem

79. To determine the nitrogen content, a sample of 0.9145 g of flour was treated with concentrated sulfuric acid, converting nitrogen into ammonium salt. By the action of alkali and blowing with air, ammonia was isolated, which was absorbed by 20 ml of hydrochloric acid solution (T (HCl) = 0.00300 g/ml). 6.30 ml of sodium hydroxide solution (T(NaOH) = 0.0025 g/ml) was used to titrate the excess. Calculate the mass fraction of nitrogen in flour.