Question

104. State the type of reaction taking place. Also balance the equation.

$\mathrm{Ca}+{\mathrm{O}}_2\to \mathrm{CaO}$

Answer 1

Step 1:- List the number of atoms of a different element present in the unbalanced equation

Element	Number of atoms in reactant	Number of atom in product
Ca	1	1
O	2	1

Step 2:- Start balancing with the compound that contains a maximum number of atoms (reactant or product)

• In this CaO has maximum no of the atom and after that check which element has a maximum number of atoms.
• There is Oxygen (O₂) that has a maximum number of atoms. check if it is balanced or not.
• Start balancing of oxygen

Atoms of oxygen	In reactant	In product
Initial	(2 in O2 )	(1 in CaO)
Final (Balanced)	(2 in O2 ) = 2 oxygen atoms	2 x (1 in CaO) = 2 oxygen atoms

Now oxygen is balanced

Step 3:- Write the balanced chemical equation

• Calcium is automatically balanced when Ca is multiplied by 2

So, the balanced chemical equation can be written as:

$\underset{\mathbf{Calcium}}{\mathbf{2}\mathbf{Ca}}\mathbf{+}\underset{\mathbf{Oxygen}}{{\mathbf{O}}_{\mathbf{2}}}\mathbf{\to }\underset{\mathbf{Calcium}\mathbf{}\mathbf{oxide}}{\mathbf{2}\mathbf{CaO}}$

Step 4:- Identify the type of reaction

Combination reaction is the reaction in which two or more reactant combine to form a single product. So in the reaction, Calcium combine with Oxygen to form Calcium oxide (CaO).

Therefore,$\underset{\mathbf{Calcium}}{\mathbf{2}\mathbf{Ca}}\mathbf{+}\underset{\mathbf{Oxygen}}{{\mathbf{O}}_{\mathbf{2}}}\mathbf{\to }\underset{\mathbf{Calcium}\mathbf{}\mathbf{oxide}}{\mathbf{2}\mathbf{CaO}}$ is a combination reaction