Question

Prin evaporarea apei, 0,5 kg solutie de CaCl₂de concentratie 10% ajunge la o concentratie de 25%. Cate grame de apa s-au evaporat ?

Answer 1

c1=10%
c2=25%
md- masa dizolvata (va ramane acceasi)
ms1,ms2- masa de solutie

c1=md*100/ms1
md=c1*ms1/100
md=0.05 kg CaCl2

c2=md*100/ms2
ms2=md*100/c2
ms2=0.2 kg solutie CaCl2

stim ca ms=md+mH2O
atunci:

(1): mH20=ms1-md=0.5-0.05=0.45 kg H20
(2): mH20=ms2-md=0.2-0.05=0.15 kg H20 
deci masa de apa evaporata va fi

0.45-0.15=0.3 kg