Question

Ce cantitate de alcool trebuie adaugata la 50 g de solutie de alcool de concentratie 25 % pentru a ajunge la o cantitate de 40% alcool?

Answer 1

ms=50g
c=25%
c1=40%
md2=masa de alcool adăugată $c = \frac{md}{ms} \times 100 \\ md = \frac{c \times ms}{100} \\ md = \frac{25 \times 50}{100} = 12.5g$
$c1 = \frac{md + md2}{ms + md2} \times 100 \\ c1(ms + md2) = 100(md + md2)$
c1×ms+c1×md2=100×md+100×md2
c1×ms-100×md=100×md2-c1×md2
md2 (100-c1)=c1×ms-100×md$md2 = \frac{c1 \times ms - 100 \times md}{100 - c1}$
$md2 = \frac{40 \times 50 - 100 \times 12.5}{100 - 40}$
$md2 = \frac{2000 - 1250}{60} = \frac{750}{60} = 12.5g$