100 ml, 0.1 M ${\text{K}}_{\text{2}}{\text{SO}}_{\text{4}}$ is mixed with 100 ml, 0.1 M ${\text{Al}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$ solution. The resultant solution

 is 

${\text{K}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{\hspace{0.17em}+\hspace{0.17em}Al}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$

$\left[{\text{SO}}_{\text{4}}^{\text{2-}}\right]\text{\hspace{0.17em}=}\frac{\text{0.1\hspace{0.17em}×\hspace{0.17em}100\hspace{0.17em}+\hspace{0.17em}0.1\hspace{0.17em}×\hspace{0.17em}3\hspace{0.17em}×\hspace{0.17em}100}}{\text{200}}\text{\hspace{0.17em}=\hspace{0.17em}0.2\hspace{0.17em}M}$

$\text{Normality\hspace{0.17em}of\hspace{0.17em}}\left[{\text{SO}}_{\text{4}}^{\text{2-}}\right]\text{\hspace{0.17em}=\hspace{0.17em}0.2\hspace{0.17em}×\hspace{0.17em}2\hspace{0.17em}=\hspace{0.17em}0.4\hspace{0.17em}N}$