29.5 mg of organic compound containing nitrogen was digested according to Kjeldahl's method and the evolved ammonia was absorbed in 20mL of 0.1 M HCl solution. The excess of the acid required 15m

Question

29.5 mg of organic compound containing nitrogen was digested according to Kjeldahl's method and the evolved ammonia was absorbed in 20mL of 0.1 M HCl solution. The excess of the acid required 15mL of 0.1M NaOH solution for complete neutralisation. The percentage of nitrogen in the compound is

TestHub · Accepted Answer

Weight of organic compound = 29.5 mg NH 3 + HCl → NH 4 Cl HCl + NaOH → NaCl + H 2 O (Remaining) 15 × 0.1 M = 1.5 mmol Total millimole of HCl = 2 Millimole used by N H 3 = 2 - 1.5 = 0.5 Weight of N H 3 = 0.5 × 17 mg = 8.5 mg Weight of nitrogen = 14 17 × 8.5 m g = 7 m g % N i t r o g e n = 7 29.5 × 100 = 23.7 %

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