JEE Main · 2022 · 29 Jun 2022 · Shift 1 · Practical and Analytical Chemistry

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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

1 M H_{2} SO_{4}

solution. The percentage of nitrogen in the compound is ____. (Nearest integer)

Answer: 64

Solution

In Kjeldahl's method, the ammonia produced neutralizes the acid. Using the neutralization equation:

Milliequivalents of H₂SO₄ = milliequivalents of NH₃

12.5 \times 1 \times 2 = 25 meq

Since NH₃ is monoacidic, 25 meq = 25 millimoles of NH₃ = 25 millimoles of N.

Mass of nitrogen:

Mass of N = 25 \times 1 0^{- 3} \times 14 = 0.35 g

Percentage of nitrogen:

% N = \frac{0.35}{0.55} \times 100 = 63.6 \approx 64%

Answer: 64

JEE Main · 2022 · 29 Jun 2022 · Shift 1 · Integer answer

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