Calculate the ionic strength of the 1:2 electrolyte \mathrm{CuCl}_{2}, again of concentration 0.01~{\mathrm{mol~dm}}^{-3}.
Inserting charges in Equation (7.31):
I=\frac{1}{2}\{[C{ u}^{2+}]\times(+2)^{2}+[C{ l}^{-}]\times(-1)^{2}\}
I=\frac{1}{2}\sum_{i=1}^{i=i}c_{i}z_{i}^{2} (7.31)
We next insert concentrations. In this case, there are two chloride ions formed per formula unit of salt, so [Cl^{-}]=2\times[\mathrm{CuCl}_{2}], but only one copper, so [Cu^{2+}]=[\mathrm{CuCl}_{2}].
I=\frac{1}{2}\{([\mathrm{CuCl}_{2}]\times4)+(2[\mathrm{CuCl}_{2}]\times1)\}
so we obtain the result I = 3 × c for this, a 1:2 electrolyte. And, I=0.03\ \mathrm{mol~dm}^{-3} because [{ C u C l}_{2}]=0.01~\mathrm{mol~dm}^{-3}.