In a chemical reaction, a two directional arrow indicates
that the chemical reaction is reversible. A single directional arrow in a
chemical reaction always indicates that it is an irreversible reaction. By a
reversible chemical reaction, it means that the compound that is formed after
reaction can be again broken down to form the compounds from which it was made.
In case of irreversible chemical reaction it is not possible to return to the
previous state from which the compound was made.
