Class 10 Science

Chemical Equation Class 10 Science

These notes are based on the chapter Chemical Reactions and Equations from NCERT book based on CBSE syllabus.

Writing a chemical reaction in sentences can be cumbersome. There is an easier way to write chemical reaction and that is through chemical equation.

Chemical equation can be written as word equation or by using symbols of elements. Following is the word equation of combustion of magnesium.

Magnesium + Oxygen → Magnesium oxide

Word equation can be lengthy and cumbersome. So, the better way to write a chemical equation is by using symbols of elements. Above equation can be written as follows:

Mg + O2 → MgO

Substances written on the LHS (Left Hand Side) of the arrow are called reactants, as they participate in chemical reaction. Substances written on the RHS are called products, as they are made after a chemical reaction.

Reactant and Product in Chemical Equation

Reactant: Substances which take part in a chemical reaction are called reactants.

Product: New substance formed after a chemical reaction is called product.

Example: A + B → C + D

In this equation, A and B are called reactants and C and D are called the products. Arrow shows the direction of chemical reaction. Condition, if any, is written generally above the arrow.

Example: When hydrogen reacts with oxygen, it gives water. This reaction can be represented by following chemical equation.

Hydrogen + Oxygen → Water

H2 + O2 → H2O

In first equation words are used and in second symbols of substances are used to write the chemical equation. For convenience, symbol of substance is used to represent chemical equations. In this case, hydrogen and oxygen are reactants, while water is the product.

Example: When coal is burnt in air, it gives carbon dioxide and energy. Coal is mainly composed of carbon. In this reaction, carbon reacts with oxygen to give carbon dioxide.

Carbon + Oxygen → Carbon dioxide + Heat

Above is a word equation.

C + O2 → CO2 + Heat

Above is chemical equation with symbols of reactants and products.

Example: When zinc reacts with sulphuric acid, the chemical reaction gives zinc sulphate and hydrogen gas.

Zinc + Sulphuric Acid → Zinc sulphate + Hydrogen

Above is a word equation.

Zn + H2SO4 → ZnSO4 + H2

Above is chemical equation with symbols of reactants and products.

Example: When calcium reacts with water, calcium hydroxide and hydrogen are formed. In this reaction, calcium and water are reactants, while calcium hydroxide and hydrogen are products.

Calcium + Water → Calcium Hydroxide + Hydrogen

Ca + 2H2O → Ca(OH)2 + H2

Example: When iron reacts with copper sulphate, the chemical reaction gives iron sulphate and copper.

Iron + Copper Sulphate → Iron Sulphate + Copper

Above is a word equation.

Fe + CuSO4 → FeSO4 + Cu

Above is chemical equation with symbols of reactants and products.

Chemical Equation is a way to represent the chemical reaction in concise and informative way.