You might have noted that when copper powder is heated in a Chine dish of copper powder becomes coated with black colour substance.
(i) How has this black-colored substance formed?
(ii) What is that black substance?
(iii) Write the chemical equation of the reaction that takes place.

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Solution

1) The black coloured substance is formed due to the reaction of Cu with air.
2) Copper reacts with oxygen present in air to form copper oxide, which is black in colour. The black substance is the copper oxide.
3) $2 C u + O_{2} \to 2 C u O$

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(e) Quick lime reacts vigorously with water releasing a large amount of heat.
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(a) Explain the following in terms of gain or loss of oxygen with one example each :

(i) oxidation (ii) reduction

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You might have noted that when copper powder is heated in a Chine dish of copper powder becomes coated with black colour substance.(i) How has this black-colored substance formed?(ii) What is that black substance?(iii) Write the chemical equation of the reaction that takes place.

1) The black coloured substance is formed due to the reaction of Cu with air. 2) Copper reacts with oxygen present in air to form copper oxide, which is black in colour. The black substance is the copper oxide.3) 2Cu+O2→2CuO

You might have noted that when copper powder is heated in a Chine dish of copper powder becomes coated with black colour substance.
(i) How has this black-colored substance formed?
(ii) What is that black substance?
(iii) Write the chemical equation of the reaction that takes place.

1) The black coloured substance is formed due to the reaction of Cu with air.
2) Copper reacts with oxygen present in air to form copper oxide, which is black in colour. The black substance is the copper oxide.
3) $2 C u + O_{2} \to 2 C u O$