If the law of conservation of matter is to be kept, it means that there must be the same number of atoms in each half of the equation. There must be the same number of atoms in reactants and in the products.

The law of conservation of matter states that matter is neither created nor destroyed in the course of chemical reaction. This is the main reason why the number of atoms of products must balance those of reactions and vice versa.

So, the equation:

Na+H_{2}O=Na0H+H_{2}isconsideredunbalanceandhencenotacceptable.

This has to be balanced as:

2Na+2H_{2}0=2Na0H_{ (}_{a}_{q)}+ H_{2(g)}

S=solid L=Liquids Aq=aqueous g=gas

**WRITING CHEMICAL EQUATIONS**

Chemical equations are written using chemical symbols and formulae. It is necessary to have as much detail as possible about what is going on in are action e.g. **hydrogen** gas reacts with oxygen gas to produce **water**.

We translate this information to a word equation.

**Hydrogen** (gas)+Oxygen gas = **water**

(Reactants) (Product)

2H_{2}+0_{2} 2H_{2}0

Balanced equation

Common chemical reactions include (a) Combustion of hydrocarbons (b) Neutralization reactions (c) Double decomposition

Examples:

- C
_{3}H_{8}+0_{2}C0_{2}+H_{2}0 - HCl+Na0H NaCl+H
_{2}0 - AgN0
_{3}+NaCl AgCl+NaN0_{3}

**BALANCE CHEMICAL EQUATIONS**

aN_{2}+bH_{2}=cNH3

N: 2a =C……(i)

H: 2b =3C…..(ii)

Let a=1

From equation (i) 2 (1) = C

2 = C C = 2

From equation (ii ) 2b =3 (2)

2b = 6

B =3

A =1, b=3 C=2

N_{2}+3H_{2}=2NH_{3}

Two methods are commonly employed in chemical equations:

- Balancing by inspection.
- Balancing by the use of simultaneous equations.

See also