Question

How can I balance the equation:
$Pb{\left( {OH} \right)_2}{\text{ + HCl }} \to {\text{ PbC}}{{\text{l}}_2}{\text{ + }}{{\text{H}}_2}{\text{O}}$

Answer 1

A balanced chemical equation is one in which the atomicity of elements on the reactant side is equal to the product side. Thus we have to make the atomicity of elements on both sides equal. We will start balancing the hydrogen and oxygen and then balance the whole reaction.

Complete answer:
A reaction is said to be balanced when the atomicity of the same element on both sides is equal. The balanced chemical reaction follows the law of equal proportions. Thus we can balance the above reaction in the following ways:
$(i)$ Start with balancing the hydrogen atoms and oxygen atoms.
$Pb{\left( {OH} \right)_2}{\text{ + HCl }} \to {\text{ PbC}}{{\text{l}}_2}{\text{ + }}{{\text{H}}_2}{\text{O}}$
$(ii)$ Since there are two oxygen atoms at reactant therefore replace ${H_2}O$ with $2{H_2}O$ .
$Pb{\left( {OH} \right)_2}{\text{ + HCl }} \to {\text{ PbC}}{{\text{l}}_2}{\text{ + 2}}{{\text{H}}_2}{\text{O}}$
$(iii)$ Now there are four hydrogen atoms at product side, it can be balanced as:
$Pb{\left( {OH} \right)_2}{\text{ + 2HCl }} \to {\text{ PbC}}{{\text{l}}_2}{\text{ + 2}}{{\text{H}}_2}{\text{O}}$
Now check for $Pb$ and $Cl$ which are already balanced. Thus the above reaction is now a balanced reaction. Thus the balanced chemical equation will be:
$Pb{\left( {OH} \right)_2}{\text{ + 2HCl }} \to {\text{ PbC}}{{\text{l}}_2}{\text{ + 2}}{{\text{H}}_2}{\text{O}}$
Now we can observe that the atomicity of elements is the same as in reactants and products. Therefore the reaction is said to be a balanced chemical reaction. Now the reaction will also follow the law of equal proportions.

Note:
Since it is a neutralization reaction, it is recommended to balance the water molecule first for neutralization reactions. The coefficients of the compounds cannot be a rational number, if it is a rational then do convert into integer by applying multiplication or division. Also the coefficient cannot be in negative form. At last we can check the balanced chemical reaction by checking the atomicity of elements at both sides.