Question

The given equation represents the reaction of sodium metal with water.

$\mathrm{Sodium}+\mathrm{Water}\to \mathrm{Sodium}\mathrm{hydroxide}+\mathrm{Hydrogen}$

Which of the following chemical equations represents a complete balanced equation for the given word equation?

• A. $2\mathrm{Na}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$
• B. $\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\to \mathrm{NaOH}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\left(\mathrm{g}\right)$
• C. $2\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\left(\mathrm{g}\right)$
• D. $2\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

Answer 1

The correct option is D

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

The explanation for the correct option:

Balanced equation

The equation in which the number of atoms of all the molecules is equal on both sides of the equation is known as a balanced chemical equation.

The balanced equation for the reaction of sodium metal with water-

(D) $2\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

The explanation for the incorrect options

(A) $2\mathrm{Na}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

In this chemical equation, only one oxygen atom$\left(\mathrm{O}\right)$ is present on the reactant's side whereas there are 2 oxygen atoms present on the product's side, so it is an unbalanced equation.

(B) $\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\to \mathrm{NaOH}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\left(\mathrm{g}\right)$

In this chemical equation, 2 oxygen atoms are present on the reactant's side whereas there is only 1 oxygen atom present on the product's side, so it is an unbalanced equation.

(C) $2\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\left(\mathrm{g}\right)$

In this chemical equation, there are 4 hydrogen atoms$\left(\mathrm{H}\right)$ present on the reactant's side but there are 6 hydrogen atoms present on the product's side, so it's also an unbalanced equation.

Hence, option (D) is the correct option with a balanced equation.