Question

answer with explanation

Answer 1

Explanation:

Question :-

The order of pKa value of the following acid is

(I) 2-hydroxybenzoic acid

(II) 4-hydroxybenzoic acid

(III) 2,4-Dihydroxy Benzoic acid

(IV) 2,5-Dihydroxybenzoic acid

Solution :-

As we know that :-

• Ka is inversely proportional to pKa
• The lower the pKa value, the stronger the acid.

Now,

Here most acidic is 2,5-Dihydroxybenzoic acid .

Order of Decreasing acidic order :-

2,5-Dihydroxybenzoic acid > 2,4-Dihydroxy Benzoic acid > 2-hydroxybenzoic acid > 4-hydroxybenzoic acid

(Here 2,5-Dihydroxybenzoic acid and 4-hydroxybenzoic acid least acidic)

Now,

As we know that :-

• If the acid is stronger than its pKa value will be less

Then,

Here, 4-hydroxybenzoic acid is least acidic

It means,

pKa value of 4-hydroxybenzoic acid is more.

Similarly,

The order of pKa value of acids is

II > I > III > IV

Hence,

Option C is correct