How can balance the chemical equation

Steps Involved in Balancing a Chemical Equation:

Consider  the  chemical  reaction  between  magnesium  and  oxygen  to  understand  the  steps  involved  in balancing a chemical equation.

Step 1:

Let us first write the word equation for this reaction.

Magnesium + Oxygen → Magnesium oxide

Step 2:

Write the chemical equation for the reaction between magnesium and oxygen.

Mg + O2 → MgO

Step 3:

Count the number of atoms of an element occurring on both L.H.S. and R.H.S. in this equation.

Mg + O2 → MgO

This is an unbalanced equation.

Step 4:

To balance a chemical equation, first draw boxes around each formula. Do not change anything inside the boxes while balancing the equation. 

Choose  a  reactant  or  a  product which has  the  maximum  number  of  atoms  in  it. 

In that compound, select the element which has the maximum number of atoms. In this equation we shall select MgO i.e. magnesium oxide and the element oxygen in it.

To balance the oxygen atoms, let us multiply magnesium oxide molecule by 2 on the right hand side.

Step 5:

There  are  two  oxygen  atoms  on  either  side  of  the  equation  but  one  magnesium  atom  on  the  reactant's side and two on the product's side. Therefore, multiply the magnesium atom by 2 on the left hand side.

Therefore, the number of atoms of each element of reactants = The number of atoms of each element of products.

Step 6: Writing Specific Conditions on the Arrow

The reaction is carried out in the presence of ‘Heat’. On heating, magnesium combines with oxygen present in air to form magnesium oxide.

Step 7: Writing Symbols of Physical States

The various ways in which a chemical equation can be made more informative are : (i) By indicating the physical states of the reactants and products. Example: Solid state is indicated by the symbol (s).

(ii) By indicating the heat changes taking place in the reaction. For Example: An exothermic reaction is indicated by writing “+Heat” or “+Heat energy” or “+Energy” on the products side of an equation.

(iii) By indicating the “conditions” under which the reaction takes place.

Example: Delta stands for heat which is written on the arrow sign in the equation.