Chemistry
In the laboratory preparation of hydrogen from zinc & dilute hydrochloric acid - state a reason for
(a) Addition of traces of copper [II] sulphate to the reaction medium.
(b) Collecting the hydrogen by downward displacement of water and not air & collecting it after all the air in the apparatus is allowed to escape.
(c) Having the end of the thistle funnel dip below the level of the acid in the flask.
Hydrogen
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Answer
(a) Addition of traces of copper [II] sulphate to the reaction medium enhances the speed of the reaction.
(b) Hydrogen forms a highly explosive mixture with air. Hence, it is not collected by the downward displacement of air and collected only after all the air in the apparatus is allowed to escape. As it is almost insoluble in water, so it is collected by downward displacement of water.
(c) The lower end of the thistle funnel should dip below the level of the acid in the flask, otherwise hydrogen gas produced will escape through thistle funnel.
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