105. State the type of reaction taking place. Also balance the equation.
${\mathrm{CuSO}}_4+\mathrm{NaOH}\to \mathrm{Cu}{\left(\mathrm{OH}\right)}_2+{\mathrm{Na}}_2{\mathrm{SO}}_4$

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

The given chemical equation is as follows:

${\mathrm{CuSO}}_4+\mathrm{NaOH}\to \mathrm{Cu}{\left(\mathrm{OH}\right)}_2+{\mathrm{Na}}_2{\mathrm{SO}}_4$

Element	Number of atoms in reactant	Number of atom in product
Cu	1	1
S	1	1
O	5	6
Na	1	2
H	1	2

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

• In this Na₂SO₄ 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

Atoms of oxygen	In reactant	In product
Initial	(4 in CuSO4 ) and (1 in NaOH) = 5	(2 in Cu(OH)2) and ( 4 in Na2SO4) = 6
Final (Balanced)	(4 in CuSO4 ) +2 x (1 in NaOH) =6	(2 in Cu(OH)2) + ( 4 in Na2SO4) = 6

Now oxygen is balanced.

Step 3:- Write the balanced chemical equation

• Sodium(Na), sulphur (S), and Hydrogen (H₂) are already automatically balanced.

So, the balanced chemical equation is as follows:

$\underset{\mathrm{Copper}\mathrm{sulphate}}{{\mathrm{CuSO}}_4}+\underset{\mathrm{Sodium}\mathrm{hydroxide}}{2\mathrm{NaOH}}\to \underset{\mathrm{Copper}\mathrm{hydroxide}}{\mathrm{Cu}{\left(\mathrm{OH}\right)}_2}+\underset{\mathrm{Sodium}\mathrm{sulphate}}{{\mathrm{Na}}_2{\mathrm{SO}}_4}$

Step 4:- Identify the type of reaction

Double displacement reaction is the reaction in which two reactants react by the exchange their ions to form two new compounds. So, here Sulphate group exchange with sodium to form sodium sulphate and hydroxide combine with copper to form copper sulphate

Therefore, $\underset{\mathbf{Copper}\mathbf{}\mathbf{sulphate}}{{\mathbf{CuSO}}_{\mathbf{4}}}\mathbf{}\mathbf{+}\underset{\mathbf{Sodium}\mathbf{}\mathbf{hydroxide}}{\mathbf{2}\mathbf{NaOH}}\mathbf{}\mathbf{\to }\mathbf{}\underset{\mathbf{Copper}\mathbf{}\mathbf{hydroxide}}{\mathbf{Cu}{\mathbf{\left(}\mathbf{OH}\mathbf{\right)}}_{\mathbf{2}}}\mathbf{}\mathbf{+}\mathbf{}\underset{\mathbf{Sodium}\mathbf{}\mathbf{sulphate}}{{\mathbf{Na}}_{\mathbf{2}}{\mathbf{SO}}_{\mathbf{4}}}$is a Double displacement reaction.