Question

The following reactions all occur in a blast furnace. Which of these are redox reactions?

$\begin{array}{r}l(a)3F{e}_2{O}_3(s)+CO(g)\to 2F{e}_3{O}_4(s)+C{O}_2(g)\\ (b)F{e}_3{O}_4(s)+CO(g)\to 3FeO(s)+C{O}_2(g)\\ (c)FeO(s)+CO(g)\to Fe(l)+C{O}_2(g)\\ (d)C(s)+O_2(g)\to C{O}_2(g)\\ (e)C(s)+C{O}_2(g)\to 2CO(g)\\ (f)CaC{O}_3(s)+CaO(s)\to C{O}_2(g)\\ (g)CaO(s)+Si{O}_2(s)\to CaSi{O}_3(l)\end{array}$

Short answer

Answer is,

1. This is a redox reaction.
2. This is a redox reaction.
3. This is a redox reaction.
4. This is a redox reaction.
5. This is a redox reaction.
6. This is not a redox reaction.
7. This is not a redox reaction.

Step-by-step solution

Oxidation agent:

A redox reaction can be defined as a chemical reaction in which electrons are transferred between two reactants participating in it. It can be identified by observing the changes in the oxidation states of the reacting species.

checking redox reaction for (a):

a)

$3F{e}_2{O}_3(s)+CO(g)\to 2F{e}_3{O}_4(s)$

All oxidation states of oxygen are -2

Which mean oxidation state of Fe changes from +3 to$+\frac{8}{3}$and C changes from +2 to +4

The redox reaction:

Oxidation:$C^{2+}-2e^{-}\to C^{4+}$

Reduction: $6F{e}^{3+}+2e^{-}\to 6F{e}^{+\frac{8}{3}}$

checking redox reaction for (b):

b)

$F{e}_3{O}_4(s)+CO(g)\to 3FeO(s)+C{O}_2(g)$$$

All oxidation states of oxygen are -2

Which mean oxidation state of Fe changes from$+\frac{8}{3}$to +2and C changes from +2 to +4

The redox reaction:

Oxidation:$C^{2+}-2e^{-}\to C^{4+}$

Reduction: $3F{e}^{\frac{98}{3}+}+2e^{-}\to 3F{e}^{3+}$

checking redox reaction for (c):

c)

$FeO(s)+CO(g)\to Fe(l)+C{O}_2(g)$$$

All oxidation states of oxygen are -2

Which mean oxidation state of Fe changes from +2 to 0 and C changes from +2 to +4

The redox reaction:

Oxidation:$C^{2+}-2e^{-}\to C^{4+}$

Reduction: $F{e}^{2+}+2e^{-}\to F{e}^0$

checking redox reaction for (d):

d)

$C(s)+O_2(g)\to C{O}_2(g)$$$

All oxidation states of c changes from 0 to +4 and of O changes from 0 to -2.

The redox reaction:

Oxidation:$C^0-4e^{-}\to C^{4+}$

Reduction: $2O^0+4e^{-}\to 2O^{2-}$

checking redox reaction for (e):

e)

$C(s)+C{O}_2(g)\to 2CO(g)$$$

All oxidation states of oxygen are -2

An oxidation states of c changes from 0 to +2 and from +4 to 0+2.

The redox reaction:

Oxidation:$C^0-2e^{-}\to C^{2+}$

Reduction: $C^{4+}+4e^{-}\to C^{2+}$

checking redox reaction for (f):

f)

$CaC{O}_3(s)+CaO(s)\to C{O}_2(g)$$$

All oxidation states of oxygen are -2 of Ca are +2 and of C are +4

This is not a redox reaction.

checking redox reaction for (g):

g)

$CaO(s)+Si{O}_2(s)\to CaSi{O}_3(l)$$$

All oxidation states of oxygen are -2 of Ca are +2 and of Si are +4

This is not a redox reaction.