Given, Molarity of CrO42−(M1)=0.154M Molarity of S2O32−(M2)=0.25M Volume of S2O32−(V2)=40mL Volume of CrO42−(V1)= ? CrO4+S2O3⟶SO42−+Cr(OH)4+6 Gram equivalent of CrO42−= Gram equivalent of S2O32− N1V1=N2V2 Normality = Molarity ×n factor n for Cr=6−3=3 n for S⇒S2O32−⟶2SO42−+8e− =8 0.154×3×V1=0.25×40×8 V1=173mL