Question

When sodium metal is added to water, it gets

• A. reduced
• B. oxidised
• C. hydrolysed
• D. remains unchanged

Answer 1

The correct option is B

oxidised

• Oxidation means the loss of electrons, in this oxidation state increases.
• Reduction means the gain of electrons, in this oxidation state decreases.
• The one who gets oxidised acts as a reducing agent and the one who gets reduced acts as an oxidising agent.
• Reaction of sodium with water:

$2\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$
Sodium Water Sodium hydroxide Hydrogen

• Here oxidation state of $\mathrm{Na}$ in $\mathrm{Na}$ is $0$ and that of $\mathrm{H}$ in ${\mathrm{H}}_2\mathrm{O}$ is $+1$ at the reactant side but the oxidation state of $\mathrm{Na}$ in $\mathrm{NaOH}$ is $+1$ and that of $\mathrm{H}$ in ${\mathrm{H}}_2$ is $0$ at the product side.
• So, we can say that $\mathrm{Na}$ is getting oxidised since its oxidation number is increasing from $0$ to $+1$ and ${\mathrm{H}}_2\mathrm{O}$ is getting reduced since its oxidation number is decreasing from $+1$ to $0$.
• The one who gets oxidised acts as a reducing agent and the one who gets reduced acts as an oxidising agent.
• So here $\mathrm{Na}$ is a reducing agent and ${\mathrm{H}}_2\mathrm{O}$is an oxidising agent.

So when sodium metal is added to water it gets oxidised.

The correct option is Option B oxidised.