JEE MAIN - Chemistry (2014 (Offline) - No. 3)
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 M/10 sulphuric acid. The unreacted acid required 20 ml of M/10
sodium hydroxide for complete neutralization. The percentage of nitrogen in the compound is:
3%
5%
6%
10%
Explanation
$$\% \,\,$$ of $$\,\,N = {{1.4\,\, \times \,\,meq.of\,\,acid} \over {mass\,\,of\,\,organic\,\,compound}}$$
meq. of $$\,\,{H_2}S{O_4} = 60 \times {M \over {10}} \times 2 = 12$$
meq. of $$\,\,NaOH = 20 \times {M \over {10}} = 2$$
$$\therefore$$ meq. of acid consumed $$ = 12 - 2 = 10$$
$$\therefore$$ $$\,\,\,\% \,\,\,$$ $$N = {{1.4 \times 10} \over {1.4}} = 10\% $$
meq. of $$\,\,{H_2}S{O_4} = 60 \times {M \over {10}} \times 2 = 12$$
meq. of $$\,\,NaOH = 20 \times {M \over {10}} = 2$$
$$\therefore$$ meq. of acid consumed $$ = 12 - 2 = 10$$
$$\therefore$$ $$\,\,\,\% \,\,\,$$ $$N = {{1.4 \times 10} \over {1.4}} = 10\% $$
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