Van't Hoff factor of 80% dissociated uni-trivalent electrolyte solution is

They all are classified as ‘A₃B’ type(uni-trivalent) electrolytes…..${\mathrm{A}}_3\mathrm{B} \rightleftharpoons 3{\mathrm{A}}^{+}+{\mathrm{B}}^{3-} ;$ n=4

Examples….M₃PO₄

                     Van't Hoff factor, i = $1-\mathrm{\alpha }+\mathrm{n\alpha }$ ;

    when n= 4

                    Van't Hoff factor, i = $1+3\mathrm{\alpha }$ ; 

i = 1 + 3(0.8)=3.4