In the following schematic diagram for the preparation of hydrogen gas, what would happen if following changes are made?
Answer: (a) When zinc dust is taken instead of zinc granules to react with sulphuric acid, the hydrogen gas is formed. But the rate of reaction increases in the case of zinc dust compared to the zinc granules, because of increase in surface area as increase in surface are increases the rate of reaction. Thus, when zinc dust is used in the place of zinc granules, hydrogen gas is produced at a faster rate.
(b) Zinc granules give hydrogen gas; along with zinc chloride; when they react with hydrochloric acid.
Zn + 2HCl ⇨ ZnCl2 + H2O
Thus, when hydrochloric acid is used at the place of sulphuric acid, zinc chloride is formed in place of zinc sulphate; along with hydrogen gas and reaction takes place at the same rate.
(c) Copper does not react with dilute acids in normal condition because copper lies at lower position in reactivity series and is considered as a noble metal.So, if copper turning is taken in place of zinc granules, no reaction will take place.
(d) If sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated, sodium zincate is formed along with hydrogen gas. But heating of test tube will increase the rate of formation of hydrogen gas as heating of reaction mixture increases the rate of reaction.
Zn + 2NaOH ⇨ Na2ZnO2 + H2
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