Question - The pH of 0.1 M monobasic acid is 4.50. Calculate the concentration of H+, A- and HA. Also determine the values of ka and pka of mono basic acid.
Dear Student,
The pH of 0.1 M monobasic acid is 4.50. Calculate the concentration of H+, A- and HA. Also determine the values of ka and pka of mono basic acid.
As we know that pH = -log[H+] = 4.5
[H+] = Antilog [-4.5]
[H+] = 3.16*10-5
HA H+ + A-
[H+] = 3.16*10-5 = [A-]
HA H+ + A-
Initial conc. 0.1 0 0
At eq. [HA] = (0.1-3.16*10-5)
0.1>>3.16*10-5
So 3.16*10-5 can be neglected in comparison to 0.1
So [HA] = 0.1 mol
Ka = [H+] [A-] / [HA]
Ka = (3.16*10-5 )2/0.1 = 1.0* 10-8
pKa = -log Ka
pKa = -log (1.0* 10-8 )
pKa = 8
Hope it helps!