Question: On heating blue coloured powder of copper (II) nitrate in a boiling tube, black copper oxide, O2 and a brown gas X is formed.
(a) Identify the type of reaction and the gas X.
(b) Write balanced chemical equation of the reaction.
(c) Write the pH range of aqueous solution of the gas X. [CBSE OD, Set 1, 2019]
Answer: (a) Decomposition reaction The gas X is nitrogen dioxide (NO₂)
(b) 2Cu(NO₃)₂·3H₂O + ∆ → 2 CuO + 4 NO₂↑ + O₂↑ + 6H₂O
(c) Oxides of non-metals are acidic. Therefore aqueous solution of NO₂ would be acidic. The pH would be less than 7 or 6.9.