Question

Which reactions are oxidation-reduction reactions?

1. FeS(s) + 2HCl(aq) → H2S(g) + FeCl2(g)

2. AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3

3. 2C3H6(g) + 9O2(g) → 6CO2(g) + 6H2O(g)

4. Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g)

Answer 1

3 and 4 are oxidation and reduction reactions.
for 3, the carbon in C3H6 lost hydrogen and gained oxygen which results in it being oxidised
in 4, Fe2O3 is reduced by CO to form Fe

Answer 2

Answer: The correct answer is Option 3 and Option 4.

Step-by-step explanation:

Redox reactions are termed as the reactions in which reduction and oxidation reactions occur simultaneously.

Reduction reactions are the ones where a substance gains electrons. The oxidation state of the substance gets reduced.

Oxidation reactions are the ones where a substance looses electrons. The oxidation state of the substance is increased.

Fro the given options:

Option 1:
`FeS(s)+2HCl(aq.)\rightarrow H_2S(g)+FeCl_2(g)`

This reaction is a type of double displacement reaction because exchange of ions takes place.

Option 2:
`AgNO_3(aq.)+NaCl(aq.)\rightarrow AgCl(s)+NaNO_3`

This reaction is a type of double displacement reaction because exchange of ions takes place.

Option 3:
`2C_3H_6(g)+9O_2(g)\rightarrow 6CO_2(g)+6H_2O(g)`

On reactant side:

Oxidation state of Carbon = +2

Oxidation state of Oxygen = 0

On product side:

Oxidation state of Carbon = +4

Oxidation state of Oxygen = -2

Here, oxidation state of carbon is increasing from +2 to +4. Thus, it is getting oxidized and oxidation state of oxygen is getting reduced from 0 to -2. Thus, it is getting reduced.

Option 4:
`Fe_2O_3(s)+3CO(g)\rightarrow 2Fe(l)+3CO_2(g)`

On reactant side:

Oxidation state of Iron = +3

Oxidation state of Carbon = +2

On product side:

Oxidation state of Iron = 0

Oxidation state of Carbon = +4

Here, oxidation state of carbon is increasing from +2 to +4. Thus, it is getting oxidized and oxidation state of iron is getting reduced from +3 to 0. Thus, it is getting reduced.

Hence, the correct answer is Option 3 and Option 4.