Bantu Jawab Guys pakai Cara No.1 dan 2 Iyaa

[1] m urea = 12 gram
Mr urea = Ar C + Ar O + 2 Ar N + 4 Ar H
= 12 + 16 + 2(14) + 4(1)
= 60
n urea = m / Mr
= 12 gr / 60
= 0,2 mol

m air = 90 gram
Mr air = 2 Ar H + Ar O
= 2(1) + 16
= 18
n air = m / Mr
= 90 gr / 18
= 5 mol

n total = n urea + n air
= 0,2 mol + 5 mol
= 5,2 mol

X urea = n urea / n total
= 0,2 mol / 5,2 mol
= 0,03846


[2]

% urea = 10%
Mr urea = 60
Mr air = 18

Asumsikan :
m tot = 100 gram
m urea = 10 gram
m air = 90 gram

n urea = m / Mr
= 10 gr / 60
= 1/6 mol

n air = m / Mr
= 90 gr / 18
= 5 mol

n tot = n air + n urea
= 5 mol + 1/6 mol
= 5 1/6 mol

X urea = n urea / n tot
= 1/6 mol / 5 1/6 mol
= 1/31 = 0,03226