Write word equations and then balanced equations for the reaction taking place when:
(a) Dilute sulphuric acid reacts with zinc granules.
(b) Dilute hydrochloric acid reacts with magnesium ribbon.
(c) Dilute sulphuric acid reacts with aluminium powder.
(d) Dilute hydrochloric acid reacts with iron filings.

Hint:A metal reacts with sulphuric acid to form metal sulphate and hydrogen gas. A metal reacts with hydrochloric acid to form metal chloride and hydrogen gas.

Complete answer:
(a) Dilute sulphuric acid reacts with zinc granules to form zinc sulphate and hydrogen.
First write the word equation:
\[{\text{Sulphuric acid + Zinc }} \to {\text{ Zinc sulphate + Hydrogen}}\]
Now write the balanced equation:
\[{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}\left( {aq} \right){\text{ + Zn}}\left( s \right){\text{ }} \to {\text{ ZnS}}{{\text{O}}_4}\left( {aq} \right){\text{ + }}{{\text{H}}_2}\left( g \right)\]

(b) Dilute hydrochloric acid reacts with magnesium ribbon to form magnesium chloride and hydrogen.
First write the word equation:
\[{\text{Hydrochloric acid + magnesium }} \to {\text{ magnesium chloride + Hydrogen}}\]
Now write the balanced equation:
\[{\text{2HCl}}\left( {aq} \right){\text{ + Mg}}\left( s \right){\text{ }} \to {\text{ MgC}}{{\text{l}}_2}\left( {aq} \right){\text{ + }}{{\text{H}}_2}\left( g \right)\]

(c) Dilute sulphuric acid reacts with aluminium powder to form aluminium sulphate and hydrogen.
First write the word equation:
\[{\text{Sulphuric acid + aluminium }} \to {\text{ aluminium sulphate + Hydrogen}}\]
Now write the balanced equation:
\[{\text{3}}{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}\left( {aq} \right){\text{ + 2Al}}\left( s \right){\text{ }} \to {\text{ A}}{{\text{l}}_2}{\left( {{\text{S}}{{\text{O}}_4}} \right)_3}\left( {aq} \right){\text{ + 3}}{{\text{H}}_2}\left( g \right)\]

(d) Dilute hydrochloric acid reacts with iron filings to form ferric chloride and hydrogen..
First write the word equation:
\[{\text{Hydrochloric acid + Iron }} \to {\text{ Ferric chloride + Hydrogen}}\]
Now write the balanced equation:
\[{\text{6HCl}}\left( {aq} \right){\text{ + Fe}}\left( s \right){\text{ }} \to {\text{ 2FeC}}{{\text{l}}_3}\left( {aq} \right){\text{ + 3}}{{\text{H}}_2}\left( g \right)\]

Note: In the above reactions, the protons accept electrons to form hydrogen gas. Thus, sulphuric acid or hydrochloric acid is reduced during the reaction. Gain of electrons is reduction. Metal is oxidized to metal ions in the salt as metal loses electrons to form metal cations. The loss of electrons is oxidation. Thus, above reactions represent redox reactions in which sulphuric acid or hydrochloric acid acts as oxidizing agent and metal acts as reducing agent.