Hydrogen gas is evolved when dilute hydrochloric acid is added to a reactive metal. When iron reacts with dilute H2SO4, iron (II) sulphate with the evolution of hydrogen gas is formed.

Gas produced when dilute hydrochloric acid is added to reactive metal:

When dilute hydrochloric acid (HCl) is added to a reactive metal, hydrogen gas (H2) is produced. This is a common reaction that occurs between an acid and a metal.

Explanation:

When an acid reacts with a metal, a displacement reaction takes place, where the metal displaces hydrogen from the acid. In the case of hydrochloric acid, the reaction can be represented by the following equation:

2HCl + Zn → ZnCl2 + H2

In this equation, HCl represents hydrochloric acid, Zn represents the reactive metal zinc, ZnCl2 represents zinc chloride (a salt), and H2 represents hydrogen gas.

Reaction process:

The reaction occurs due to the reactivity of the metal with the acid. The acid molecules dissociate into hydrogen ions (H+) and chloride ions (Cl-) in water. When the metal is added to the acid, the metal atoms lose electrons and form positive ions. These metal ions then react with the hydrogen ions from the acid to produce hydrogen gas. The chloride ions from the acid combine with the metal ions to form a salt.

Key points:

- Dilute hydrochloric acid (HCl) is commonly used in this reaction.
- Reactive metals, such as zinc, iron, magnesium, and aluminum, can participate in this reaction.
- The reaction is a displacement reaction, where the metal displaces hydrogen from the acid.
- Hydrogen gas (H2) is produced as a result of this reaction.
- The chloride ions from the acid combine with the metal ions to form a salt.

Conclusion:

When dilute hydrochloric acid is added to a reactive metal, such as zinc, a displacement reaction occurs. Hydrogen gas is produced as the metal displaces hydrogen from the acid. This reaction is commonly used to generate hydrogen gas in the laboratory and industrial processes.