Derive defination and explain common ion effect by example .

1.	Derive defination and explain common ion effect by example .
Answer» Solution :EXAMPLE of common ion effect : Consider an example of acetic acid dissociation EQUILIBRIUM REPRESENTED as : `CH_3COOH_((aq)) hArr H_((aq))^(+) + CH_3COO_((aq))^(-)` `Hac_((aq)) hArr H_((aq))^(+) + Ac_((aq))^(-)` `therefore` Ionization constant `K_a=([H^+][Ac^-])/([HAc])` Addition of acetate ions to an acetic acid solution results in decreasing the CONCENTRATION of Hydrogen ions `[H^+]`. The equilibrium shifts towards the formation of dissociate acid. If the `H^+` ions are added from an external source then the equilibrium moves in the direction of undissociated acetic acid i.e., in a direction of reducing `[H^+]` . This phenomenon is an example of common ion effect. Definationof common ion effect :"It can be defined as a shift in equilibrium on adding a substance that provides more of an ionic SPECIES already present in the dissociation equilibrium. Thus, we can say that common ion effect". The common ion effect is a phenomenon based on the Le-Chatelier.s principle.

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