Chemistry > Chemical Equilibrium > 1.0 Introduction
Chemical Equilibrium
1.0 Introduction
2.0 Chemical Equilibrium
3.0 Law of mass action
4.0 Equilibrium Constant
5.0 Important Relationship Involving Equilibrium Constant
6.0 Reaction Quotient ($Q$) and prediction of direction of reaction
7.0 Relationship Between $\Delta {G^ \circ }\ and\ K$
8.0 Factors Affecting Equilibrium (Le-Chatelier's Principle)
1.1 Types of Chemical Reactions
Chemical Reactions are divided into two categories:
1. Irreversible Reaction: The reactions in which reactants are completely converted into products and do not attain equilibrium are called irreversible reactions. They are represented by single arrow $\left( \to \right)$.
For example: Combustion reaction is irreversible reaction because it proceed in one direction only.
$${C_x}{H_y} + {O_2} \to C{O_2} + {H_2}O$$
2. Reversible Reaction: In reversible reactions, the reactants and products are never fully consumed i.e., reactants form products and products also react to form reactants in backward direction. They are represented by double arrow $\left( \rightleftharpoons \right)$ or $\left( \rightleftarrows \right)$.
For example: The reaction $$A + B\mathop \rightleftharpoons \limits_{k'}^k C + D$$ can be written as
$$\begin{equation} \begin{aligned} {\text{Reaction 1: }}A + B\mathop \to \limits^k C + D \\ {\text{Reaction 2: C}} + D\mathop \to \limits^{k'} A + B \ \end{aligned} \end{equation} $$ In reversible reactions, both the reactions are occurring simultaneously.
Further, reversible reactions are divided into two types:
(a) Molecular Reactions: Reactions which involve molecules as reactants and products. For example: $${H_2}(g) + {I_2}(g) \rightleftharpoons 2HI(g)$$
(b) Ionic Reactions: Reactions which involve ions along with molecules as reactants and products. For example: $$C{H_3}COOH \rightleftharpoons C{H_3}CO{O^ - } + {H^ + }$$
