Odpowiedź :
Z def. stęż. procent.
60g subst------40g wody (100g roztworu - 60g subst)
xg subst--------180g wody
x = 270g subst.
Cp=60%
mw=180g
ms=?
Cp=ms/(ms+mw) * 100%
60%=ms/(ms+180g) * 100% /*(ms+180g)
60ms+10800g=100ms
40ms=10800g /:40
ms=270g