Kjeldahl's method was used for the estimation of nitrogen in an organic compound. The ammonia evolved from 0.55 g of the compound neutralised 12.5 mL of 1M H$$_2$$SO$$_4$$ solution. The percentage of nitrogen in the compound is ______ (Nearest Integer)

We need to find the percentage of nitrogen in the compound using Kjeldahl's method. The mass of the organic compound is 0.55 g, and 12.5 mL (0.0125 L) of H$$_2$$SO$$_4$$ solution of molarity 1 M was used to neutralise the ammonia. Thus, the moles of H$$_2$$SO$$_4$$ used are 1 × 0.0125 = 0.0125 mol.

The reaction of ammonia with sulfuric acid is $$2NH_3 + H_2SO_4 \rightarrow (NH_4)_2SO_4$$, so 1 mole of H$$_2$$SO$$_4$$ reacts with 2 moles of NH$$_3$$ and the moles of NH$$_3$$ that reacted are 2 × 0.0125 = 0.025 mol. Each mole of NH$$_3$$ contains 1 mole of nitrogen, giving 0.025 mol of nitrogen whose mass is 0.025 × 14 = 0.35 g. Therefore, the percentage of nitrogen is $$\% N = \frac{0.35}{0.55} \times 100 = 63.6\% \approx 64\%$$. The percentage of nitrogen in the compound is 64%.