For the estimation of nitrogen, 1.4 g of organic compound was digested by Kjeldahl method and the evolved ammonia was absorbed in 60 mL of $\frac{\mathrm{M}}{10}$ sulphuric acid. The unreacted acid required 20 ml of $\frac{\mathrm{M}}{10}$ sodium hydroxide for complete neutralization. The percentage of nitrogen in the compound is:

JEE Main · 2014 · 06 Apr 2014 · Offline · Practical and Analytical Chemistry

For the estimation of nitrogen, 1.4 g of organic compound was digested by Kjeldahl method and the evolved ammonia was absorbed in 60 mL of

\frac{M}{10}

sulphuric acid. The unreacted acid required 20 ml of

\frac{M}{10}

sodium hydroxide for complete neutralization. The percentage of nitrogen in the compound is:

Answer: (D)

Work in milliequivalents. The acid taken is

60 \times \frac{1}{10} \times 2 = 12

meq, the factor of two because sulphuric acid is dibasic. The leftover acid neutralised by alkali is

20 \times \frac{1}{10} \times 1 = 2

meq, so the ammonia consumed

12 - 2 = 10

meq of acid, which is

10

meq of nitrogen. That nitrogen weighs

10 \times 14/1000 = 0.14

g, and against the

1.4

g sample it is

\frac{0.14}{1.4} \times 100 = 10%

JEE Main · 2014 · 06 Apr 2014 · Offline · Single correct option