Answer:
a) 2,4-dinitrobenzoic acid: the most acidic compound, p-nitrobenzoic acid: _______, p-bromobenzoic acid: the least acidic compound
b) oxalic acid: the most acidic compound, acetic acid: the least acidic compound, formic acid: _______.
c) p-cyanobenzoic acid: the least acidic compound, benzoic acid: the most acidic compound, p-aminobenzoic acid: _______.
Step-by-step explanation:
a) 2,4-dinitrobenzoic acid is the most acidic compound of this set because it has two strong electronegative substituents (nitrogen dioxide) which increases the acidity of benzoic acid, while p-bromobenzoic acid is the least acidic compound because bromine is a weaker electron withdrawing group than nitrogen dioxide.
b) The presence of 2 -COOH group makes Oxalic acid the most acidic compound of this set, while decrease in acidity of carboxylic acid due to the presence of methyl group on carbon of -COOH group makes acetic acid the least acidic compound of this set.
(c) Benzoic acid has a higher acid dissociation constant value (4.45 Ka) therefor it is the most acidic compound of this set, while p-cyanobenzoic acid is the least acidic compound of this set as it has the least acid dissociation constant value (16 Ka).