A sample of of a neutral -amino acid (A) generated exactly of gas at standard temperature and pressu — Biomolecules Chemistry Question
Question
A sample of $0.89\text{ g}$ of a neutral $\alpha$ -amino acid (A) generated exactly $0.224\text{ L}$ of $N_2$ gas at standard temperature and pressure (STP) upon quantitative reaction with nitrous acid ($HNO_2$). Determine the molar mass of the unknown amino acid in g/mol.
Answer: 89
💡 Solution & Explanation
Aliphatic primary amines (like the $\alpha$ -amino group) react quantitatively with $HNO_2$ to release exactly 1 mole of $N_2$ gas per mole of amine. Moles of $N_2 = \frac{0.224\text{ L}}{22.4\text{ L/mol}} = 0.01\text{ mol}$. This corresponds to $0.01\text{ mol}$ of the amino acid. Molar mass = $\frac{0.89\text{ g}}{0.01\text{ mol}} = 89\text{ g/mol}$ (indicating the amino acid is Alanine).
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