Question

A solution is obtained by mixing 300g of 25% solution and 400g of 40% solution by mass . Calculate the mass percentage of the resulting solution.

Answer 1

300x25%= 75
and 400x40%= 160
therefore mass of solute=160+75
= 235gm
mass of solution= 300+400=700gm
%mass=235/700 x 100
=235/7 = 33.2%

Answer 2

Mass of solute (1) = 300g × 25/100
                              = 75g

Mass of solute (2) = 400g ×40/100
                              = 160g

Total masss of solute = 75+160
                                   = 235g

Total mass of solution = 300 + 400
                                    = 700g

% composition by mass of solute = mass of solute / total mass of solution ×100
                                                      = 235/700 ×100
                                                      = 33.57% of solute

% composition by mass of solvent = 100 - 33.57
                                                       = 66.43%

Hope it helps...