In the following schematic diagram for the preparation of hydrogen gas as shown in the figure, what would happen if the following changes are made?
(a) In place of zinc granules, same amount of zinc dust is taken in the test tube.
(b) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.
(c) In place of zinc, copper turnings are taken.
(d) Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.
When same amount of zinc dust is taken in the test tube in place of zinc granules, the reaction rate is comparatively faster because zinc dust has larger surface rea than zinc granules. Also the hydrogen gas will evolve with greater speed when zinc dust is used in place of zinc granules.
(b) With dilute hydrochloric acid, zinc chloride is formed instead of zinc sulphate. Almost same amount of hydrogen gas is evolved in both the cases.
Zn + 2HCl ⇨ ZnCl2 + H2O
(c) If copper turnings are taken instead of zinc, no reaction will take place. Hydrogen gas will not evolve. This is because copper does not react with dilute acids of H2SO4 or HCl under normal conditions because copper lies at lower position in the reactivity series.
(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. Heating of test tube will just increase the rate of reaction thus increasing the formation of hydrogen gas.
