Class 11 Chemistry - Chapter Equilibrium NCERT Solutions | It has been found that the pH of a 0.01M

Welcome to the NCERT Solutions for Class 11th Chemistry - Chapter Equilibrium. This page offers a step-by-step solution to the specific question from Excercise ".$ex_no." , Question 47: it has been found that the ph of a 0 01m solution....
Question 47

It has been found that the pH of a 0.01M solution of an organic acid is 4.15. Calculate the concentration of the anion, the ionization constant of the acid and its pKa.

Answer

Let the organic acid be HA.

⇒ HA H + A-

Concentration of HA = 0.01 M

pH = 4.15

-log[H+] = 4.15

[H+]  = 7.08x10-5

Now, Ka = [H+] [A-]  / [HA] 

[H+]  = [A-]  = 7.08x10-5

[HA]  = 0.01

Then,

Ka =  7.08x10-5 x 7.08x10-5  /  0.01

Ka =  5.01x10-7

pKa = -log Ka

        =  -log(5.01x10-7)

pKa = 6.3001

 

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