Question

Write the balanced chemical equation for: When Sodium metals react with water to give Sodium hydroxide and hydrogen gas.

Answer 1

Balanced chemical equation:

A chemical equation in which the number of atoms of each element on both sides of the equation is equal is called a balanced chemical equation.

Balancing of a chemical equation by hit and trial method:

Step: 1: Representation of chemical reaction:

When Sodium metals react with water, it gives Sodium hydroxide and hydrogen gas.

$\underset{\mathrm{Sodium}}{\mathrm{Na}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{cold}\right)\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Sodium}\mathrm{hydroxide}}{\mathrm{NaOH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}+\mathrm{Heat}(∆)$

Step: 2: Calculating atoms on each element on both the sides of the reaction:

Elements	Number of atoms on the reactant side	Number of atoms on the product side
Na	1	1
H	2	3
O	1	1

Step: 3: Balancing the uneven numbers of atoms on the reactant and product sides:

To balance hydrogen on both the sides we will add 2 against $\left({\mathrm{H}}_2\mathrm{O}\right)$ on a reactant side and 2 against $\left(\mathrm{NaOH}\right)$ on a product side. $\underset{\mathrm{Sodium}}{\mathrm{Na}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{cold}\right)\mathrm{Water}}{2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Sodium}\mathrm{hydroxide}}{2\mathrm{NaOH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}+\mathrm{Heat}(∆)$

Elements	Number of atoms on the reactant side	Number of atoms on the product side
Na	1	2
H	4	4
O	2	2

To balance $\left(\mathrm{Na}\right)$ now, we will add 2 against$\left(\mathrm{Na}\right)$ on the reactant side.

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

As the number of atoms on both sides is equal thus, the equation is called a balanced equation.

Hence, a balanced equation is :

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