larutan NaOH 80% (Mr=40g/mol) memiliki fraksi mol pelarut sebesar...

Sifat Koligatif
Konsentrasi dalam Molal

Misalkan massa total larutan 100 gram
Maka massa NaOH = 80% x 100 gram = 80 gram
Massa air = 100 gram - 80 gram = 20 gram

Mr NaOH = 40
Mr air = 18

mol NaOH = 80/40 = 2 mol
mol air = 20/18 = ¹⁰/₉ mol

Fraksi mol pelarut

Xp = mol air / [mol air + mol NaOH]

Xp = [¹⁰/₉] / [¹⁰/₉ + 2]
Kalikan 9 atas dan bawah per

Xp = 10 / [10 + 18]

Xp = ¹⁰/₂₈
Sederhanakan

Jadi Xp = ⁵/₁₄