Q. 114.1( 12 Votes )
What happens when:
(a) copper powder is heated in a china dish?
(b) hydrogen gas is passed over hot copper (II) oxide?
(a)When copper powder is heated in the presence of air (oxygen), copper reacts with oxygen to form copper oxide. The copper
oxide formed is black in colour. The black colour is formed due to the oxidation of copper takes place.
The chemical equation of the reaction that takes place is given below:
2Cu + O2→ 2CuO
(b) When hydrogen gas is passed over hot copper oxide, the black coating on the surface turns brown as the reverse reaction takes place and copper is obtained.
The reaction that takes place is:
CuO + H2 → Cu + H2O
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Which among the following statement(s) is(are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to:
(i) The formation of silver by decomposition of silver chloride
(ii) Sublimation of silver chloride
(iii) Decomposition of chlorine gas from silver chloride
(iv) Oxidation of silver chlorideEvergreen Science
Which of the following are exothermic processes?
(i) Reaction of water with quicklime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)Evergreen Science