Question

Write the balanced chemical equation for the reaction between calcium carbonate and hydrochloric acid to form calcium chloride, carbon dioxide, and water.

Answer 1

A balanced chemical equation follows the law of conservation of mass that states that the number of atoms should be equal on the reactant side and product side.

1. The given equation is:

$$\begin{gathered} {\mathrm{CaCO}}_3\left(\mathrm{s}\right)+\mathrm{HCl}\left(\mathrm{g}\right)\to {\mathrm{CaCl}}_2\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Calcium}\mathrm{Hydrochloric}\mathrm{Calcium}\mathrm{Carbon}\mathrm{water} \\ \mathrm{carbonate}\mathrm{acid}\mathrm{Chloride}\mathrm{dioxide} \end{gathered}$$

2. After calculating the number of atoms on the reactant and product side:

Atoms	On reactant side	On product side
Calcium	1	1
Carbon	1	1
Oxygen	3	3
Hydrogen	1	2
Chlorine	1	2

Here, we can see that Hydrogen and Chlorine are not balanced.

3. The balanced chemical equation can be written by changing the stoichiometric coefficient and which is adding 2 to $\mathrm{HCl}$ on reactant side.

${\mathrm{CaCO}}_3\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{g}\right)\to {\mathrm{CaCl}}_2\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

4. This chemical equation is now balanced, as the number of atoms is equal on both sides.