The description of a chemical reaction in sentences is quite long and time consuming. To make it shorter, a chemical reaction can be written in word equation form.
For e.g. – When a magnesium ribbon burns in air / oxygen, it gives magnesium oxide.
Word equation –
Magnesium + Oxygen → Magnesium Oxide
This word equation can be made more useful, shorter, concise and informative by using chemical formulae and symbols instead of words.
Mg + O2 → MgO
Thus, a chemical equation represents a chemical reaction.
Terms Used in Chemical Equation -.
(i) Reactants –
The chemical substances (One or more) that undergo chemical changes in the reaction are called reactants. In the above reaction, magnesium and oxygen are reactants.
(ii) Products –
The new chemical substances ( one or more ) formed as a result of chemical reaction are called products. Magnesium oxide is product in the above example.
- A chemical reaction or change of reactants into products involves chemical rearrangement of atoms by breaking of old bonds and making of new bonds.
- When there are two or more reactants/ products, they are written with a plus sign (+) among them.
(iii) Arrow –
In a chemical equation, reactants and products are separated by an arrow sign.
- The head of an arrow always indicates toward products and shows the direction of the reaction. Whereas, the arrow tail point indicates toward reactants.
- In general, the reactants are written on the left hand side (L.H.S.) and the products are written on the right hand side (R.H.S.)
Reactants → Products
A complete chemical equation compiles reactants, products, their physical states (g, l or s ) and other conditions such as heat changes, temperature required, catalyst, pressure etc. at one place in symbols.
Balanced and unbalanced Chemical Equations