Q39 of 44 Page 8

On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed

(a) Write a balanced chemical equation of the reaction.


(b) Identity the brown gas X evolved.


(c) Identity the type of reaction.


(d) What could be the pH range of aqueous solution of the gas X?


(a) 2Cu(NO3)2 → 2Cu + 4NO2 + O2



(b) The brown gas 'X' has to be nitrogen dioxide.



(c) This type of reaction falls under the category of Decomposition reactions.



(d) The pH of the aqueous solution of gas X would be less than 7.
The oxides of non metals are generally acidic in nature. Therefore, their aqueous solutions would exhibit acidic nature.


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Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why?

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A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.

(a) Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.


(b) Name the black substance formed and give its chemical formula.

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Give the characteristic tests for the following gases

(a) CO2


(b) SO2


(c) O2


(d) H2

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What happens when a piece of

(a) zinc metal is added to copper sulphate solution?


(b) aluminium metal is added to dilute hydrochloric acid?


(c) silver metal is added to copper sulphate solution?


Also, write the balanced chemical equation if the reaction occurs.