All the chemical equations must balance, because atoms are neither created nor destroyed in chemical reactions. A chemical equation in which the numbers of atoms of different elements on the reactants side (left side) are same as those on product side (right side) is called a balanced reaction.

Balancing a chemical equation involves finding out how many formula units of each substance take part in the reaction. A formula unit, as the name implies, is one unit – whether atom, ion, or molecule – corresponding to a given formula. One formula unit of NaCl for example is one Na+ ion and one Cl- ion; one formula unit of MgBr2 is one Mg+ ion and two Br- ions and one formula unit of H2O is one H2O molecule.

**Chemical reactions and Equations**

Complicated chemical equations need to be balanced using a systematic method, but simple equations can be balanced using a mixture of common sense and trial and error.

Now let us balance the chemical equation using a systematic method.

Step 1: Write the unbalanced equation using the correct chemical formula for each reactant and products. In the reaction of hydrogen with oxygen to yield water, you can write unbalanced chemical equations as

follow:

H2 + O2 - H2O……………(6)

Step 2: Compare number atoms of each element on both sides. Find

the suitable coefficients – the numbers placed before formula to indicate

how many formula units of each substance are required to balance the

equation. Only these coefficients can be changed when balancing an

equation, the formulas themselves can’t be changed. We take the

reaction of hydrogen with oxygen as an example; we can balance the

equation by adding a coefficient of 2 to both H2 and H2O. By so doing

there are 4 hydrogen and 2 oxygen atoms on each side of the equation:

2H2 + O2 - 2H2O …………..(7)

Step 3: Reduce the coefficients to their smallest whole number values,

if necessary by dividing them all by a common devisor.

Step 4: Check the answer by making sure that the numbers and kinds

of atoms are the same on both sides of the equation.

Let us work out some examples to see how equations are balanced.

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