Reactants and products coexist in equilibrium so that reactant conversion to product is always less than 100%. Equilibrium reactions may involve the decomposition of a covalent (non-polar) reactant or ionization of ionic compounds into their ions in polar solvents.
In this section, we will learn about the ionic equilibrium in ionic solutions. Substances in Ionic Equilibrium can be classified into two categories on the basis of their ability to conduct electricity given as under,
These are substances that consist of molecules that bear no electric charge, do not dissociate into their constituent ions and thus do not conduct electricity in their aqueous solution or molten state. For example sugar solution.
These are substances that dissociate into their constituent ions in their aqueous solution and thus conduct electricity in their aqueous solutions or molten state. Example, salt solution, acid solution, base solution etc.
Electrolytes in ionic equilibrium can be further classified into strong and weak electrolytes.
Strong electrolytes are substances that upon dissociation in their ionic solution ionize completely while in the case of weak electrolytes, the dissociation is partial in nature.
For example, NaCl undergoes complete ionization in its aqueous solution to render sodium ions (Na+) and chloride (Cl–) ions, whereas, acetic acid undergoes partial ionization to render some amount of acetate ions(CH3COO–) and hydrogen(H+) ions.
- In case of a strong electrolyte, the dissociation reaction is said to be complete, thus moving in the forward direction only, whereas, in case of a weak electrolyte, the reaction is said to be reversible in nature.
- In the case of the weak electrolyte, the equilibrium is established between the ions and the unionized molecules, which can be termed as ionic equilibrium. The same can be understood with the following example.