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CBSE Class 10 Science 2019 Outside Delhi Set 1

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Question : 6 of 27
Marks: +1, -0
On heating blue coloured powder of copper (II) nitrate in a boiling tube, black copper oxide, O2\mathrm{O}_2 and a brown gas XX is formed.
(a) Identify the type of reaction and the gas X.
(b) Write balanced chemical equation of the reaction.
(c) Write the pH\mathrm{pH} range of aqueous solution of the gas XX.
Solution:  
(a) Decomposition reaction The gas XX is nitrogen dioxide (NO2)(\mathrm{NO}_2)
(b)
2 Cu(NO3)2Blue⋅3 H2O→Δ2 CuOBlack\underset{\text{Blue}}{2\,\mathrm{Cu}(\mathrm{NO}_3)_2} \cdot 3\,\mathrm{H}_2\mathrm{O} \xrightarrow{\Delta} \underset{\text{Black}}{2\,\mathrm{CuO}}+4 NO2↑+Brown gasO2↑+6 H2O+ \underset{\text{Brown gas}}{4\,\mathrm{NO}_2\uparrow +} \mathrm{O}_2\uparrow + 6\,\mathrm{H}_2\mathrm{O}
(c) Oxides of non-metals are acidic. Therefore aqueous solution of this gas would be acidic. The pH\mathrm{pH} would be less than 7 or 6.9
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