Question

Terdapat larutan NaCl 10% mempunyai p 1,1 kg/liter.Tentukan kemolalan dan fraksinya.

Answer 1

Massa larutan NaCl = 1 liter x 1,1 kg/liter = 1,1 kg
massa NaCl = 10/100 x 1,1 kg = 0,11 kg = 110 gram
Mr NaCl = 58,5 gr/mol
mol NaCl = 110 gr / 58,5 gr/mol = 1,88 mol

massa H2O = 1,1 kg - 0,11 kg = 0,99 kg = 990 gram
Mr H2O = 18 gr/mol
mol H2O = 990 gr / 18 gr/mol = 55 mol

kemolalan NaCl = 1,88 mol / 0,99 kg = 1,90 m

fraksi mol NaCl = 1,88 / (1,88+55) = 0,033
fraksi mol H2O = 55 / (1,88+55) = 0,967