Chemical Reactions and Equations

Main concepts:

Chemical Reaction

Whenever a chemical change occurs we can say that a chemical reaction has taken place

eg :

Food gets digested in our body

Rusting of iron.

Here reactants and products are involving and they participate in chemical Reaction.

We can observe or recognise a chemical reaction by observing change in state, colour, by evolution of gas or by change in temperature.

Physical state of the reactant and products are mentioned to make chemical reaction more informative.

eg: we use (g) for gas, (l) for liquid, (s) for solid and (aq) for aqueous.

Chemical Equation

A chemical reaction can be expressed symbolically by using chemical equation

eg : magnesium is burnt into air to form magnesium oxide can be represented as

Mg + O 2 MgO

Balancing chemical equation

The chemical equation in which the no. of atoms of different

elements is same on both sides of the arrow is called balanced chemical equation.

A + B C + D

balaced equation is a type of

xA + yB uC + Vd

Here x , y , u and v represents number of atoms requred to balance both side.

We balance the chemical equation so that no. Of atoms of each element

involved in the reaction remain same at the reactant

and product side.

eg Fe + H 2 O → Fe 2 O 3 + H 2 can be written as

3 Fe(s) + 4H 2 O(g) → Fe 2 O 3 (s) +4H 2 (g)