Question 16. Identify from the following reactions the reactants that undergo oxidation and reduction. a. Fe + S → FeS b. 2Ag2O → 4 Ag + O2 c. 2Mg + O2→ 2MgO d. NiO + H2→ Ni + H2O

Question 16.

Identify from the following reactions the reactants that undergo oxidation and reduction.

a. Fe + S → FeS

b. 2Ag2O → 4 Ag + O2

c. 2Mg + O2→ 2MgO

d. NiO + H2→ Ni + H2O

Answer:

a. Fe + S → FeS

In the given reaction, Fe is giving 2 electrons to Sulphur. Sulphur is accepting those electrons. This means:

⇒ Fe undergoes oxidation (to lose electrons)

⇒ Sulphur undergoes reduction (to accept electrons)

b. 2Ag2O → 4 Ag + O2

⇒ Ag in Ag2O has oxidation state= +1

Ag in Ag(s) has oxidation state = 0

This means Ag undergoes reduction

⇒ O in Ag2O has oxidation state = -2

O in O2 has oxidation state = 0

This means oxygen undergoes oxidation

c. 2Mg + O2→ 2MgO

First write the half reactions:

Mg0 → Mg2+ + 2e-

O2 + 4e-→ O2-

⇒ Oxygen goes from 0 to -2. Thus, it undergoes reduction.

⇒ Magnesium goes from 0 to +2. Thus, it undergoes oxidation

d. NiO + H2→ Ni + H2O

First write the half reactions:

2H0 - 2e-→ 2H1

Ni2+ + 2e-→ Ni0

⇒ Hydrogen goes from 0 to 1. Thus, it undergoes oxidation.

⇒ Nickel goes from 2 to 0. Thus, it undergoes reduction.