In the Dumas method for the estimation of nitrogen, an organic compound is heated with copper oxide. The evolved gases are passed over a heated copper gauze to form a gaseous mixture P (ignoring water vapour). The mixture P is then bubbled through an aqueous solution of potassium hydroxide, leaving a final unabsorbed gas Q . The identities of P and Q respectively are:

Step-by-step solution

When the organic compound is heated with copper oxide, it produces CO₂ , H₂O , N₂ , and traces of nitrogen oxides ( NO_x ). Passing this mixture over a heated copper gauze reduces the traces of NO_x to N₂ . Therefore, the gas mixture P leaving the copper gauze consists primarily of N₂ and CO₂ (ignoring the condensed water vapour). When mixture P is bubbled through aqueous potassium hydroxide ( KOH ), the CO₂ is absorbed to form potassium carbonate ( K₂CO₃ ). The final unabsorbed gas Q that is collected is pure nitr