Practical Organic Chemistry and PurificationhardNUMERICAL

In Kjeldahl's method, of an organic compound is digested and the evolved ammonia is absorbed in of .Practical Organic Chemistry and Purification Chemistry Question

Question

In Kjeldahl's method, $0.50\ \text{g}$ of an organic compound is digested and the evolved ammonia is absorbed in $50\ \text{mL}$ of $0.5\ \text{M}\ H_2SO_4$. The residual acid requires $60\ \text{mL}$ of $0.5\ \text{M}\ NaOH$ for complete neutralization. What is the percentage of nitrogen in the compound?

Answer: 56

💡 Solution & Explanation

Milli-equivalents of initial acid = $50 \times 0.5 \times 2 = 50\ \text{mEq}$. Milli-equivalents of base used = $60 \times 0.5 \times 1 = 30\ \text{mEq}$. The acid consumed by ammonia = $50 - 30 = 20\ \text{mEq}$. Percentage of Nitrogen = $\frac{1.4 \times \text{mEq of acid used}}{W} = \frac{1.4 \times 20}{0.50} = 56\%$.

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