28 points , 3 dan 5. sertakan cara

(3)
Urea memiliki rumus kimia CO(NH2)2.
1 molal urea = 1 mol urea / 1 kg pelarut
massa 1 mol urea = 1 x 60 = 60 gram = 0,06 kg
massa larutan urea = massa urea + massa pelarut = 0,06 + 1 = 1,06 kg

% massa urea = 0,06/1,06 x 100% = 5,66%

(5)
a)  X H2O = mol H2O / (mol H2O + mol CH3OH)

massa CH3OH = ρ x v = 11,3 x 0,793 = 8,96 gram
mol CH3OH = massa / Mr = 8,96 / 32 = 0,28 mol
massa larutan setelah diencerkan = ρ x v = 75 x 0,98 = 73,5 gram
massa air = massa larutan setelah diencerkan – massa CH3OH = 73,5 – 8,96 = 64,54 gram
mol air = massa / Mr = 64,54 / 18 = 3,585 mol

X H2O = mol H2O / (mol H2O + mol CH3OH) = 3,585 / (3,585 + 0,28) = 0,93

b) Molaritas
M = mol CH3OH / volume larutan (liter) = 0,28 / 0,075 = 3,73 M

c) Molalitas
m = mol CH3OH / massa air (kg) = 0,28 / 0,06454 = 4,34 m