Question

Which of the following will be the correct order of pka ?

Answer 1

From the given figures,

option 1 is correct

⇒ |>||>|||>|V

Therefore,the correct order of pka is option 1.

Answer 2

The correct order of pKa values of given compounds is I>II>III>IV

Explanation:

pKa is negative log of the acid dissociation constant (Ka).

$pK_a =-log K_a$

• For weak acids dissociation constant is very low.

• Therefore it is clear that the greater is the extent of dissociation, the greater will be the value of $K_a$.

• The greater will be the value of $K_a$, Stronger will be the acid.

• And $pK_a$ is the negative logarithm of $K_a$, it is greater for weak acids.

• Hence in given compounds the weak acid is first one and then second one which is weaker than third and intern third is weaker than fourth one.

• Hence, the correct order of $pK_a$ values is I>II>III>IV