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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.