Răspuns:
1. ms = 420 g
c = 16%
md = ?
formula generala a concentratiei procentuale :
c = md x 100 : ms
md = c x ms : 100 = 420 g x 16 :100 = 67,2 grame
2. c = 24%
md = 38 g
m apa = ?
c = md x 100 : ms
ms = md x 100 : c = 38 g x 100 : 24 = 158,33 grame solutie
masa de solutie = masa dizolvata + masa de apa
m apa = ms - md = 158,33 - 38 = 120,33 grame apa