For the estimation of nitrogen, of an organic compound was digested by Kjeldahl method and the evolv — Practical Organic Chemistry and Purification Chemistry Question
Question
For the estimation of nitrogen, $1.4\ \text{g}$ of an organic compound was digested by Kjeldahl method and the evolved ammonia was absorbed in $60\ \text{mL}$ of $0.1\ \text{M}$ sulphuric acid. The unreacted acid required $20\ \text{mL}$ of $0.1\ \text{M}$ sodium hydroxide for complete neutralization. What is the percentage of nitrogen in the compound?
Answer: 10
💡 Solution & Explanation
Initial mEq of $H_2SO_4 = 60 \times 0.1 \times 2 = 12\ \text{mEq}$. mEq of NaOH used for back titration = $20 \times 0.1 \times 1 = 2\ \text{mEq}$. Acid consumed by $NH_3 = 12 - 2 = 10\ \text{mEq}$. $\%N = \frac{1.4 \times \text{mEq}}{W} = \frac{1.4 \times 10}{1.4} = 10\%$.
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