Question

Give an example of redox reaction.

Answer 1

Redox reaction:-

• Redox reactions are reactions where oxidation and reduction reactions take place at the same time.
• These type of reactions involves electron transfer.

The reaction between Magnesium and Oxygen:-

• When magnesium is reacted with oxygen, the products formed are Magnesium oxide.
• The complete equation after balancing is:

$\underset{\mathrm{Magnesium}}{2\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Magnesium}\mathrm{oxide}}{2\mathrm{MgO}\left(\mathrm{s}\right)}$

Calculation of oxidation number of Magnesium:-

• From the balanced reaction we can see that on the reactant side, the oxidation number of Magnesium is 0
• Let us assume the oxidation number of Magnesium in $\mathrm{MgO}$be $\mathrm{x}$.
• And we know that oxygen has an oxidation state of $-2$
• Thus we can write that:

$$\begin{gathered} \mathrm{x}+(-2)=0 \\ \Rightarrow \mathrm{x}-2=0 \\ \Rightarrow \mathrm{x}=+2 \end{gathered}$$

• Therefore, Magnesium here undergoes oxidation as its oxidation number changes from 0 to +2, that is it loses 2 electrons.
• Reaction for magnesium part is:

$\underset{\mathrm{Magnesium}}{\stackrel{}{\mathrm{Mg}}\left(\mathrm{s}\right)}\to \underset{\mathrm{Magnesium}\mathrm{ion}}{{\mathrm{Mg}}^{2+}}+\underset{\mathrm{Electron}}{2{\mathrm{e}}^{-}}$ Oxidation

Oxidation number of Oxygen:-

• Magnesium atom donates these 2 electrons to oxygen atom.
• Thus Oxygen here undergoes reduction as it is gaining 2 electrons and its oxidation number changes from 0 to -2.
• Reaction for oxygen part is:

$\underset{\mathrm{Oxygen}}{\frac{1}{2}{\stackrel{}{\mathrm{O}}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Electron}}{2{\mathrm{e}}^{-}}\to \underset{\mathrm{Oxide}\mathrm{ion}}{{\mathrm{O}}^{2-}}$ Reduction

Therefore, an example of a redox reaction is the reaction between Magnesium and Oxygen:

$\underset{\mathrm{Magnesium}}{2\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Magnesium}\mathrm{oxide}}{2\mathrm{MgO}\left(\mathrm{s}\right)}$