Question

Find the activity coefficient of H⁺ in a solution containing 0.010 M HCl plus 0.040 M KClO₄. (Use Table 8-1.)

What is the pH of the solution?

Answer 1

Ionic strength (I) = C_iZ_i²

Ionic strength of the solution of 0.010 HCl and 0.040 M KClO_4.

= ( [H⁺] *1² + [Cl^-]*1² + [K⁺] *1² + [ClO₄^-] *1²]

= ( 0.010 + 0.010 + 0.040 + 0.040)

= 0.05

Now, activity coefficient of H⁺ can be calculated as

Activity coefficient of H⁺ = 0.855

Then , a_H+ = [H⁺] _H⁺

[H⁺] = 0.010 M

_H⁺ = 0.855

So, a_H⁺ = 0.010*0.855 = 0.0855

then , pH = - log a_H⁺ = - log (0.0855) = 2.068

Hence, pH of the solution is 2.068 .