Sebanyak 10 gram NaOH dilarutkan dalam 90 gram air sehingga terbentuk 100ml larutan NaOH jika Ar H=1,0=16 dan Na = 23 tentukan : A. Molaritas B. Molalitas C. Fr

Molaritas (M) = mol dalam 1 L larutan
Molalitas (m) = mol dalam 1 Kg pelarut
Fraksi mol (X) = mol dalam mol total

mol naOH = massa/mr = 10/40 = 0.25 mol
mol air = massa/mr = 90/18 = 5 mol
massa air = 90 gram = 0.09 Kg
larutan = 100 mL = 0.1 L

A. M NaOH = mol/V = 0.25 mol/0.1 L = 2.5 M
B. m NaOH = mol/massa air = 0.25 mol/0.09 Kg = 2.78 molal
C. X NaOH = mol naOH/(mol air+mol NaOH) = 0.25 mol/(5+0.25) mol = 0.048