Write the balanced equation for the following reaction.

Phosphorus reacts with chlorine to give phosphorus pentachloride.

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.

We will use the hit-trial method to balance the following equation.

Step-1: Representation of the chemical equation.

When phosphorus reacts with chlorine, it gives phosphorus pentachloride.

$\begin{array}{llll}{\mathrm{P}}_4\left(\mathrm{s}\right)& +{\mathrm{Cl}}_2\left(\mathrm{g}\right)& ⟶& {\mathrm{PCl}}_5\left(\mathrm{s}\right)\end{array}$

Step-2: Calculating atoms on both sides of the reaction:

Elements	The number of atoms on the left side	The number of atoms on the right side
$\mathrm{P}$	4	1
$\mathrm{Cl}$	2	5

Step 3: Balancing of atoms on both sides of the reaction:

To balance $\left(\mathrm{P}\right)$ on both sides, we will add ‘4’ against $\left({\mathrm{PCl}}_5\right)$.

$\begin{array}{llll}{\mathrm{P}}_4\left(\mathrm{s}\right)& +{\mathrm{Cl}}_2\left(\mathrm{g}\right)& ⟶& 4{\mathrm{PCl}}_5\left(\mathrm{s}\right)\end{array}$

Elements	The number of atoms on the left side	The number of atoms on the right side
$\mathrm{P}$	4	4
$\mathrm{Cl}$	2	20

At last, to balance $\left(\mathrm{Cl}\right)$ on both sides, we will add ‘10’ against $\left({\mathrm{Cl}}_2\right)$ on reactant side.

$\begin{array}{llll}{\mathrm{P}}_4\left(\mathrm{s}\right)& +10{\mathrm{Cl}}_2\left(\mathrm{g}\right)& ⟶& 4{\mathrm{PCl}}_5\left(\mathrm{s}\right)\end{array}$

Elements	The number of atoms on the left side	The number of atoms on the right side
$\mathrm{P}$	4	4
$\mathrm{Cl}$	20	20

We can see that equation is balanced now.

The balanced equation is:

$\begin{array}{llll}{\mathrm{P}}_4\left(\mathrm{s}\right)& +10{\mathrm{Cl}}_2\left(\mathrm{g}\right)& ⟶& 4{\mathrm{PCl}}_5\left(\mathrm{s}\right)\end{array}$