Question

Am alcool etilic absolut de concentratie 99,5 %. Cat alcool trebuie pus la 100 ml apa ca sa fie de 6 % concentratie ?

Answer 1

100 ml apa = 100 g apa (ro = 1 g/ml)

c% = 6% = mdx100/ms

=> ms = md + m.apa = a + 100

a = ms - 100

=> 6 = ax100/(100+a)

=> 6(100+a) = 100a

600 + 6a = 100a

=> a = 600/94 = 6,38 g

=> ms (alcool absolut) = ax100/99,5

=> ms = 6,38x100/99,5 = 6,415 g sol alcool absolut

daca se doreste si Vs stim ca ro alcool = 0,78 g/ml

=> Vs = ms / ro = 6,415 / 0,78 = 8,22 ml sol alcool absolut