i. These are reactions in which reactants react to form products and simultaneously products react to form reactants.
ii. They take place in both directions i.e. from left to right and from right to left.
iii. The reaction that takes place from left to right is called as forward reaction and the reaction that takes place from right to left is called as reverse reaction.
iv. They are represented by putting a double arrow (<=====>) between the reactants and the products.
v. In the beginning forward reaction is fast and reverse reaction is slow. But gradually rate of forward reaction decreases and rate of reverse reaction increases. Ultimately both the reactions take place at equal rate but in opposite directions and reaction attains equilibrium state.
vi. These reactions never complete or stop.