Question

How to solve a chemical equation? Explain with an example.

Answer 1

Let us take an example:
Balance the following equation: $H_2+O_2\to H_{2}O$
It is an unbalanced equation (sometimes also called a skeleton equation). This means that there are UNEQUAL numbers at least one atom on each side of the arrow. By the way, a skeleton equation is not wrong, it just hasn't been balanced yet. Presenting it as being balanced would be wrong.
In the example equation, there are two atoms of hydrogen on each side, BUT there are two atoms of oxygen on the left side and only one on the right side.
Remember this: A balanced equation MUST have EQUAL numbers of EACH type of atom on BOTH sides of the arrow.
An equation is balanced by changing coefficients in a somewhat trial-and-error fashion. It is important to note that only the coefficients can be changed, NEVER a subscript.
Important point: the coefficient times the subscript gives the total number of atoms.
Three quick examples before balancing the equation.
(a) $2H_2$ - there are $2\times 2$ atoms of hydrogen (a total of 4).
(b) $2H_{2}O$ - there are $2\times 2$ atoms of hydrogen (a total of 4) and $2\times 1$ atoms of oxygen (a total of 2).
(c) $2\left(N{H}_4\right)2S$ - there are $2\times 1\times 2$ atoms of nitrogen (a total of 4), there are $2\times 4\times 2$ atoms of hydrogen (a total of 16), and 2 \times 1 atoms of sulphur (a total of 2).