Identify which equations represent redox reactions, providing a name for the reaction if appropriate. For those reactions identified as redox, name the oxidant and reductant.

(a) ZnCO3 (s) ⟶ ZnO (s) + CO2 (g)

(b) 2Ga (l) + 3Br2 (l) ⟶ 2GaBr3 (s)

(c) 2H2O2 (aq) ⟶ 2H2O (l) + O2 (g)

(d) BaCl2 (aq) + K2SO4 (aq) ⟶ BaSO4 (s) + 2KCl (aq)

(e) C2H4 (g) + 3O2 (g) ⟶ 2CO2 (g) + 2H2O (l)

The correct options are: (b) 2Ga (l) + 3Br₂ (l) ⟶ 2GaBr₃ (s)

(c) 2H₂O₂ (aq) ⟶ 2H₂O (l) + O₂ (g)

(e) C₂H₄ (g) + 3O₂ (g) ⟶ 2CO₂ (g) + 2H₂O (l)

Explanation:

Redox reactions or oxidation-reduction reactions are the chemical reactions that involve simultaneous transfer of electrons and change in the oxidation states.

Oxidizing agent or oxidant gains electrons and itself gets reduced (oxidation number decreases). Whereas reducing agent or reductant loses electrons and itself gets oxidized (oxidation number increases).

(a) ZnCO3 (s) ⟶ ZnO (s) + CO2 (g)

In this reaction, the oxidation states of the species remains unchanged.

Therefore, it is not a redox reaction.

(b) 2Ga (l) + 3Br₂ (l) ⟶ 2GaBr₃ (s)

In this reaction, gallium loses electrons and gets oxidized from 0 oxidation state in Ga to + 3 oxidation state in GaBr₃. Whereas, bromine gains electrons and gets reduced from 0 oxidation state in Br₂ to - 1 oxidation state in GaBr₃. So, Ga is the reducing agent and Br₂ is the oxidizing agent.

Therefore, it is a redox reaction.

(c) 2H₂O₂ (aq) ⟶ 2H₂O (l) + O₂ (g)

Such a reaction is known as the disproportionation reaction.

In this reaction, oxygen loses electrons and gets oxidized from - 1 oxidation state in H₂O₂ to 0 oxidation state in O₂. Whereas, oxygen gains electrons and gets reduced from - 1 oxidation state in H₂O₂ to - 2 oxidation state in H₂O. So, H₂O₂ is the reducing agent and the oxidizing agent.

Therefore, it is a redox reaction.

(d) BaCl₂ (aq) + K₂SO₄ (aq) ⟶ BaSO₄ (s) + 2KCl (aq)

In this reaction, the oxidation states of the species remains unchanged.

Such a reaction is known as the double displacement reaction.

Therefore, it is not a redox reaction.

(e) C₂H₄ (g) + 3O₂ (g) ⟶ 2CO₂ (g) + 2H₂O (l)

Such a reaction is known as combustion.

In this reaction, carbon loses electrons and gets oxidized from - 2 oxidation state in C₂H₄ to + 4 oxidation state in CO₂. Whereas, oxygen gains electrons and gets reduced from 0 oxidation state in O₂ to - 2 oxidation state in H₂O and CO₂. So, C₂H₄ is the reducing agent and O₂ is the oxidizing agent.

Therefore, it is a redox reaction.