Suggest a reason for each oberservation given below.
(i)In firework ,powedered magnesium is used rather than 'magnesium ribbon.
(ii)Zinc and dilute `H_(2)SO_(4)` react much more quickly when a few drops of copper sulphate solutions are added.
(iii)Zinc and dilute `H_(2)SO_(4)` react much more quickly when a few drops of copper sulphate solutions are added.
(iii)The reaction between magnesium carbonate and dilute hydrochloric acid speeds up when some concentrated HCl is added.

Explanation

(i)In fire works.powdered magnesium is used because it has more surface area than magnesioum ribbon.Because of more surface area,powdered magnesium reacts faster than magnesium ribbon.
(ii)Zinc and dilute `H_(2)SO_(4)` react much more quickly when a few drops of copper sulphate solution is added .Copper sulphate acts as a catalyst which increases the rate of the reaction.
(iii)When concentration of the reactants increases ,the rate of the reaction also increases .So the reaction between magnesium carbonate and dilute hydrochloric acid speeds up by the addition of some concentrated HCl.