Question

(a) What is a redox reaction? Explain with an example.
(b) When a magnesium ribbon burns in air with a dazzling flame and forms a white ash, is magnesium oxidised or reduced? Why?
(c) In the reaction represented by the equation:
${\mathrm{MnO}}_2+4\mathrm{HCl}\underset{}{\to }{\mathrm{MnCl}}_2+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{Cl}}_2$
(i) name the substance oxidised.
(ii) name the oxidising agent.
(iii) name the substance reduced.
(iv) name the reducing agent.

Answer 1

(a) The reaction in which one substance gets oxidised and other gets reduced is known as redox reaction.

Example:

ZnO + C → Zn + CO

Here, C is oxidised to CO because oxygen is being added and ZnO is reduced to Zn because oxygen is being removed. Therefore, it is a redox reaction.

(b) Magnesium gets oxidised because oxygen is added to the substance (Mg). The chemical reaction is given as follows:

2Mg + O₂ → 2MgO

(c) (i) HCl is oxidised to Cl₂.

(ii) MnO₂ is the oxidising agent.

(iii) MnO₂ is reduced to MnCl₂.

(iv) HCl is a reducing agent.