What is the pH of 10-9 M HCl?
Here , [H+] for acid is < 10 -7 { which is not possible }
so,
total [H+] = 10 -7 + 10 -9
= 1.01 x 10 -7
Thus, pH = - log [H+]
= 6.99
The pH of 0.1 M HCN solution is 5.2. What is the value of the ionization constant (Ka) for the acid?
HCN being a weak acid has low ionization constant,
C = 0.1 M
pH = 5.2
thus [H+] = 10 - 5.2 = 0.1 Ic
Ic= 6.3 x 10 -5
now, Ka = Ic 2 x C [ for weak acid ]
=( 6.3 x 10 -5 )2 x 0.1
= 3.98 x 10 -10