Question

Balance the equation:
$Ca{{(OH)}_{2}}+C{{O}_{2}}\to CaC{{O}_{3}}+{{H}_{2}}O$

Answer 1

On the reactant side, calcium hydroxide and carbon dioxide are present, and on the product side calcium carbonate and water are present. First, balance the calcium and carbon atoms, then balance the hydrogen and oxygen atoms.

Complete answer:
To balance the equation means to make the number of atoms on the reactant and product side the same. The given reaction is:
$Ca{{(OH)}_{2}}+C{{O}_{2}}\to CaC{{O}_{3}}+{{H}_{2}}O$
On the reactant side, calcium hydroxide and carbon dioxide are present, and on the product side calcium carbonate and water are present. So, there are four elements involved in this reaction, i.e., calcium, carbon, hydrogen, and oxygen.
First, balance the calcium and carbon atoms, then balance the hydrogen and oxygen atoms.
Let us first balance the calcium atoms, on the reactant side there is one calcium atom in calcium hydroxide and on the product side there is 1 calcium atom in calcium carbonate. So, it is already balanced.
Now, on the reactant side, there is one carbon atom in carbon dioxide, and on the product side, there is 1 carbon atom in calcium carbonate. So, it is already balanced.
Now, on the reactant side, there are two hydrogen atoms in calcium hydroxide, and on the product side, there are two hydrogen atoms in water. So, it is also balanced.
Now, on the reactant side, there are four oxygen atoms (two in calcium hydroxide and two in carbon dioxide) and on the product side, there are four oxygen atoms (three in calcium carbonate and one in water). So, it is already balanced.
Therefore, the given reaction is the balanced reaction only.
$Ca{{(OH)}_{2}}+C{{O}_{2}}\to CaC{{O}_{3}}+{{H}_{2}}O$

Note:
If the reaction is acidic, then we balance the hydrogen atoms in the reaction by hydrogen ions and if the reaction is in a basic medium, the hydrogen and oxygen atoms are balanced with hydroxyl ions and water molecules.