Activity coefficient calculation example ,Debye-Huckel equation,ionic strength determination

Activity coefficient of any species is the ratio of chemical  activity to its molar concentration. 

We can write,
Chemical activity(a)=Activity coefficient (v)×Molar concentration(M)

We determine activity coefficient of an ion using debye huckel equation.The equation is shown below-

Q.Determine the activity coefficient of cro42- ion, Given-ionic strength =0.018M and radious of the ion=0.4 nm.

When radious of the ion is not given we use simply this equation.

Q.Determine the activity coefficient of Ce4+ion, Given ionic strength =0.08M.

Ionic strength is a measure of the concentration of ions in the solution.

The formula for determination of ionic stregth is-

Q.Determine the ionic strength of a solution contaning 0.2 M NaCl and 0.02 M MgSo4.

In some problem for determining pH we need to determine ionic strength as well as activity coefficient.

Q.Determine the PH of the a solution contaning 0.01 M Hcl and 0.001 M Nacl.