Question

Determina masa de apa care trebuie sa se evapore din 400 g de solutie de sare de concentratie 10 la suta astfel incat concentratia acesteia sa devina 16 la suta.

Answer 1

m apa evaporata = ?
$ms_{1} = 400 g$
$c_{1}$%= 10%
$c_{2}$%= 16%
 $\frac{ c_{1} }{100} = \frac{ md_{1} }{ ms_{1} }$⇔$\frac{10}{100} = \frac{ md_{1} }{400}$⇔$md_{1} = \frac{10.400}{100}$⇔$md_{1} =40g$
$\frac{ c_{2} }{100} = \frac{ md_{2} }{ ms_{2} }$⇔$\frac{16}{100} = \frac{ md_{1} }{ ms_{1}- m apa_{ev} }$⇔$\frac{16}{100}= \frac{40}{400- m apa_{ev} }$⇔ 6400- $16 m apa_{ev}$= 4000⇔ $16m apa_{ev}$= 6400-4000 ⇔ $16 m apa_{ev}$= 2400⇔ $m apa_{ev} = 150 g$