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Discuss about the hydrolysis of salt of weak acid and weak base and derive pH value of the solution. |
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Answer» Solution :(i) Consider the hydrolysis of ammonium acetate `CH_3COOH_(4(aq)) to CH_3COO^(-) (aq) +NH_4^(+) (aq)` (ii) In that CASE both the cation `(NH_4^(+)) and (CH_3COO^-)` anion have the tendency to REACT with water `CH_3COO^(-)+H_2O leftrightarrowCH_3COOH+Oh^-` `NH_4^(+)+H_2O leftrightarrowNH_4OH+H^+` (iii) the nature of the solution depends on the strength of acid (or) base i.e., if `K_a gt K_b` then the solution is ACIDIC and`pH lt 7` if `K_a lt K_b` then the solution is BASIC and pH and `pH gt 7`. IF `K_a =K_b`then the solution is neutral. (iv) the RELATION between the dissociation constant `K_a,K_b` and hydrolysis constant is given by the following expression. (v) ph of the solution `pH=7+1/2 pK_a-1/2 pK_b` |
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