Question

200 g de soda caustica de concentratie 20 % se amesteca cu x g solutie soda caustica de concentratie 40% cand se obtine o solutie de concentratie 30% . determina valoarea lui x

Answer 1

solutia 1:
ms1=200g
c1=20% 
md1=ms1*c1/100=200*20/100=40 g
solutia 2:
ms2=x
c2=40%
md2=ms2*c2/100=40x/100=0,4x
solutia 3:
ms3=ms1+ms2=200+x
md3=md1+md2=40+0,4x
c3=30%
md3=ms3*c3/100  40+0,4x=(200+x)* 30/100        x=........