S¹⁵ = 10g/100g apa
=> ms = 100+10 = 110g
c%final = md.finalx100/ms = 10x100/100 = 10%
Vs= 650 mL , ro=p = 1,05 g/mL
p = ms/Vs => ms = pxVs = 1,05x650 = 682,5 g
c1 = md1x100/ms1 => md1 = ms1xc1/100
= 682,5x3/100 = 20,475 g
md.final = md1 + md.adaugat(a) = 20,475 + a
ms.final = ms1 + a = 682,5 + a
=> 10 = (20,475+a)100/(682,5+a)
=> a = 477,75/9 = 53,083 g K2SO4 adaugat
facem proba:
md.final = 20,475 + 53,083 = 73,5583 g
ms.final = 682,5 + 53,083 = 735,583 g
=> c%final = 73,5583x100/735,583 = 10%, deci verifica calculele de mai sus
