JEE Main 2023 · Chemistry · Qualitative and Practical Chemistry · medium

350 g of an organic compound is subjected to Kjeldahl's digestion and the ammonia evolved is absorbed in 40.0 mL of 0.500 M H2SO4. The unreacted acid…

Numerical answer

0.350\ \mathrm g

of an organic compound is subjected to Kjeldahl's digestion and the ammonia evolved is absorbed in

40.0\ \mathrm{mL}

0.500\ \mathrm M

\mathrm{H_2SO_4}

. The unreacted acid requires

30.0\ \mathrm{mL}

1.00\ \mathrm M

\mathrm{NaOH}

for neutralisation. The percentage of nitrogen in the compound (atomic mass of N

=14

) is

Show answer and solution

Answer: 40

Acid taken

=40\times0.5\times2=40

meq (H

_2

_4

is dibasic). Unreacted acid

=30\times1.00=30

meq of NaOH. Acid neutralised by

\mathrm{NH_3}=40-30=10

meq, which equals

10

mmol

\mathrm{NH_3}

and hence

10

mmol N

=140

mg. Percentage

=\frac{0.140}{0.350}\times100=40\%

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