During Dumas' method, the evolved nitrogen gas is collected in a nitrometer over an aqueous solution — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

In Dumas' method, the organic compound is heated with $CuO$ in an atmosphere of $CO_2$. The resulting gases include $CO_2$, $H_2O$ vapor, and $N_2$. The concentrated $KOH$ solution efficiently absorbs the massive volume of $CO_2$ carrier gas and the combustion product $H_2O$, leaving only the free nitrogen gas ($N_2$) to be collected and measured in the upper part of the nitrometer.