JEE Main · 2022 · 25 Jul 2022 · Shift 1 · Practical and Analytical Chemistry

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While estimating the nitrogen present in an organic compound by Kjeldahl's method, the ammonia evolved from 0.25 g of the compound neutralized 2.5 mL of

2 M

H_{2} SO_{4}

. The percentage of nitrogen present in organic compound is _____.

Answer: 56

Solution

In Kjeldahl's method, the percentage of nitrogen is calculated using:

% N = \frac{1.4 \times N _{1} V _{1}}{mass of compound}

where

N_{1}

is normality of acid and

V_{1}

is volume in mL.

For

H X_{2} SO X_{4}

: Normality =

2 \times 2 = 4

N (since basicity = 2)

Actually, using molarity directly: moles of

H X_{2} SO X_{4} = 2 \times 2.5 \times 1 0^{- 3} = 5 \times 1 0^{- 3}

mol

Moles of

NH X_{3}

neutralized =

2 \times 5 \times 1 0^{- 3} = 10 \times 1 0^{- 3}

mol (since

H X_{2} SO X_{4}

is dibasic)

Mass of N =

10 \times 1 0^{- 3} \times 14 = 0.14

% N = \frac{0.14}{0.25} \times 100 = 56%

JEE Main · 2022 · 25 Jul 2022 · Shift 1 · Integer answer

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JEE Main · 2022 · 25 Jul 2022 · Shift 1 · Practical and Analytical Chemistry

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