Question

arrange the following in the increasing order of pKa values

Answer 1

PKA VALUES:

In chemistry most of the acids are weak in nature .Certain reactions are extremely slow and some extremely fast that’s why their progress can not be determined by any factor.

Those reactions that are moderately fast can be observed and their speed can be calculated. These calculations are done in terms of rate of reaction ‘ ka’ which is called the dissociation constant.

So,there exist an equilibrium between reactants and products at any time since the dissociation is not complete.

Suppose we have an example :

AH ↔ H+ + A-

Then its acid dissociation constant can be represented as

Ka = [H+][A−]/[AH]

If this acid will be strong enough then the concentration of [ H+] will be greator than concentration of [AH] then its ka will be a positive no. in the power of 10.

Whereas if it will be somewhat weaker in nature it will have higher concentration of [AH] greator than [H+] then it will have ka value neagtive in the power of 10,even sometimes it is very low. Then instead of representing in terms of ka,its { -log Ka } is more suitable that is called pka.

basically , pKa = - log Ka

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