Question

Sodium reacts with water to give sodium hydroxide and hydrogen. Write a balanced chemical equation for this reaction.

Answer 1

1. Balanced chemical equation- In a balanced chemical equation, the number of atoms of each element should be equal on both sides of the reaction.
2. The given reaction is: $\mathrm{Sodium}+\mathrm{water}\to \mathrm{Sodium}\mathrm{hydroxide}+\mathrm{Hydrogen}$
3. The chemical symbol for the reactants and products are-

Sodium	$\mathrm{Na}$
Water	${\mathrm{H}}_2\mathrm{O}$
Sodium hydroxide	$\mathrm{NaOH}$
Hydrogen	${\mathrm{H}}_2$

4. Chemical equation:

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

Element	Number of atoms on left side	Number of atoms on right side
$\mathrm{Na}$	1	1
$\mathrm{O}$	1	1
$\mathrm{H}$	2	3

As the number of $\mathrm{H}$atoms is not the same on both sides, this equation is not balanced.

5. Balancing of the equation: To balance the $\mathrm{H}$atoms, coefficient 2 is added ahead of$\mathrm{Na}$,${\mathrm{H}}_2\mathrm{O}$ and$\mathrm{NaOH}$.

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

Thus, after adding coefficients, the number of atoms of each type of element is-

Element	Number of atoms on left side	Number of atoms on right side
$\mathrm{Na}$	2	2
$\mathrm{O}$	2	2
$\mathrm{H}$	4	4

6. Balanced Equation:

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