Ionic equilibrium

Ionic equilibrium is the equilibrium established between the unionized molecules and the ions in a solution of weak electrolytes. pH is a measure of acidity or alkalinity of a solution. Acids produce hydrogen ions in solution. When a sparingly soluble salt is dissolved in water, a dynamic equilibrium is established.

The equilibrium established between the unionized molecules and the ions in the solution of weak electrolytes is called ionic equilibrium. For example, take acetic acid breaking up into acetate ions and hydrogen ions: CH3 COOH → CH3 COO- + H+ Chemical substances that can conduct electricity in their aqueous state or in molten state are called electrolytes. In pure water or in an aqueous solution, the product of concentrations of hydrogen and hydroxyl ions is a constant at a given temperature. This is called ionic product of water and is conventionally designated by Kw. The idea of the ionic product of water can be understood by looking at the autoionization reaction of water that may be expressed as: H2 O + H2 O = H3 O+ + OH- Kw = CH3 O+ COH- The value of Kw at 25°C is 1*10-14. In the study of acid base equilibria in aqueous solutions, we're primarily interested in the hydrogen ion concentration of a solution. Solutions that we deal with are usually dilute, and the hydrogen ion concentrations are some negative power of 10. pH is a measure of hydrogen ion concentration. It's a measure of the acidity or alkalinity of a solution. Aqueous solutions at 25°C with a pH less than seven are acidic, while those with a pH greater than seven are basic or alkaline. pH can be calculated using the following formula. pH = -log CH3 O+ Let's discuss how to calculate pH with an example. What will be the concentration of CH3 O+ in a solution having pH = 5.6? Solution: pH = -log CH3 O+ log [H3 O+] = -pH log [H3 O+] = -5.6 [H3 O+] = antilog (-5.6) = 2.512*10-6