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Chemistry Question on Organic Chemistry- Some Basic Principles and Techniques

A sample of 0.125 g of an organic compound when analysed by Duma’s method yields 22.78 mL of nitrogen gas collected over KOH solution at 280 K and 759 mm Hg. The percentage of nitrogen in the given organic compound is____.(Nearest integer)

Given : 1. The vapour pressure of water of 280 K is 14.2 mm Hg.

        2\. R = 0.082 L atm K–1 mol–1
Answer

Poriginal=759–14.2=744.8 mmHg\begin{array}{l}P_{original} = 759 – 14.2 = 744.8 ~\text{mmHg}\end{array}

nN2=744.8×22.78760×0.0821×280×1000 =0.000971 mol\begin{array}{l}n_{N_2}=\frac{744.8\times22.78}{760\times0.0821\times280\times1000}\\\ = 0.000971 ~\text{mol}\end{array}

Mass  ofN2=0.02719  gmMass \;of N_2 = 0.02719 \;gm

Percentage of nitrogen=0.02710.125×100=21.75≃22\begin{array}{l}\text{Percentage of nitrogen} =\frac{0.0271}{0.125}\times100=21.75\simeq 22 \end{array}