Question

Balance the equation:
$Zn+HCl\to ZnC{{l}_{2}}+{{H}_{2}}$

Answer 1

A reaction in which the number of atoms involved in a reaction is equal for each element on both the reactant side and the product side and satisfies the law of conservation of matter is known as a balanced chemical equation.

Complete answer:
In a chemical equation, there are two types of numbers, coefficients and subscripts, that determine the number of atoms and molecules.
The number of molecules of a substance that is used or produced in a chemical reaction are indicated by the coefficients.
The part of chemical formulas that depict the ratio of atoms in a molecule and determines its chemical identity are subscripts. They don’t change while balancing an equation.
- First, the unbalanced equation of the reaction is written.
$Zn+HCl\to ZnC{{l}_{2}}+{{H}_{2}}$
- Then the number of atoms of each element on the product and the reactant side is compared.
Here there is 1 atom each of zinc (Zn), hydrogen (H), and chlorine (Cl) on the reactant side whereas there is 1 atom of zinc (Zn) and 2 atoms each of hydrogen (H) and chlorine (Cl) on the product side.
- Now stoichiometric coefficient is added to the molecules containing elements that have a different number of atoms on the reactant and product side.
(Oxygen and hydrogen are balanced last.)
The most complex substance is balanced first. Here, $ZnC{{l}_{2}}$ is the most complex structure. There must be 2 atoms of chlorine (Cl) on both the product and reactant side. So
$Zn+2HCl\to ZnC{{l}_{2}}+{{H}_{2}}$
- Now we balance the coefficients of hydrogen. There are 2 atoms of hydrogen (H) on both the product and reactant side.
- Balance the polyatomic ions, if present, as a unit. This reaction has no polyatomic ions.
Since the number of atoms of each molecule is equal on both the product side as well as the reactant side, the balanced equation will be:
$Zn+2HCl\to ZnC{{l}_{2}}+{{H}_{2}}$

Note:
It should be noted that the above reaction is a redox reaction i.e., a reaction in which electrons are transferred between two species. The number of electrons gained and the number of electrons lost are equal in a balanced redox reaction.