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State reasons for the following :

(i) Monochloroethanoic acid has a higher pKa value than dichloroethanoic acid.

(ii) Ethanoic acid is a weaker acid than benzoic acid.

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(i) The strength of an acid is indicated by pKa value, where, pKa = – log Ka

Since monochloroethanoic acid is weaker than dichloroethanoic acid so it has lower value of dissociation constant Ka.

Therefore, it has higher value of pKa.

(ii) The —COOH group in benzoic acid is attached to sp2 - carbon of the phenyl ring and is more acidic than acetic acid in which —COOH group is attached to sp3 – carbon atom of CH3 group. So, benzoic acid is stronger than acetic or acetic acid is weaker acid than benzoic acid.

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