Question

Pure zinc is not used in the laboratory preparation of hydrogen.

Answer 1

Pure zinc is not used in the laboratory preparation of hydrogen.

Reason: The reaction of pure zinc with hydrochloric acid is very slow.

• Instead of pure zinc, zinc granules are used because they always contain copper (Cu) as an impurity which will help as a catalyst for the reaction.
• Zinc in granular form has a much larger surface area because of which reaction becomes faster.

Catalyst: The substance which speeds up the rate of reaction.

Therefore, zinc granules are used because it contains copper (Cu) catalyst which will speed up the reaction, which was otherwise slow with pure zinc.

Zn (granules) + 2HCl (aq) $\to$ ZnCl₂ (s) + H₂ (g)