Di dalam 100 ml larutan natrium hidroksida terlarut 2,8 gram NaOH, (Ar Na = 23, O = 16, H = 1). Hitunglah : a. Molaritas Larutan b. Fraksi Mol Larutan

V larutan = 100 ml
massa NaOH = 2.8 gram
BM NaOH = 23 + 16 + 1 = 40 g/mol

mol NaOH
= massa / BM
= 2.8 g / 40 g/mol
= 0.07 mol

A. Molaritas Larutan
M
= mol / Vlarutan
= 0.07 mol / 100 ml
= 0.07 mol / 0.1 lt
= 0.7 M

B. Fraksi Mol Larutan (Maksudnya NaOH?)
Asumsi:
- NaOH dilarutkan dalam air (H2O)
- Massa jenis larutan = massa jenis air = 1 g/ml
BM H2O = 2x1 + 16 = 18 g/mol

Massa larutan
= 100 ml x 1 g/ml
= 100 g

Massa air
= 100 g - 2.8 g
= 97.2 g

Mol air
= 97.2 g / 18 g/mol
= 5.4 mol

Fraksi mol NaOH
= molNaOH / molTotal
= 0.07 / (0.07 + 5.4)
= 0.013

Semoga membantu :)