Question

Hitunglah fraksi mol urea dalam larutan urea 20%. (Mr urea = 60)

Answer 1

Xurea/ CO(NH2)2 = n urea / n urea + nair

20 % massa urea dalam 100 % larutan
sehingga massa urea = 20 gr
massa pelarut/air = 100-20 = 80 gr


jadi n urea = massa urea/Mr
= 20/60 = 0,33

n air = massa air/Mr
=80/18 = 4,44


jadi X urea = n urea/ nurea + n air
= 0,33 / 0,33 + 4,44
=0,33/4,77
= 0,069
dibulatkan menjadi 0,07

Answer 2

20%= 20 urea, 80 gr air
Xt= nt/ nt+np
=0,3/0,3+8
=0,03