Question

What is the molality of a 10.5% by mass glucose (C6H12O6) the density of the solution is 1.03 g/ml.

Answer 1

Mass water = 100 g solution - 10.5 g glucose => 89.5 g of H2O

Molar mass glucose => 180.1559 g/mol

Molality = moles glucose / kg solvent

( 10.5 / 180.1559 ) mol / ( 89.5 / 1000 ) kg =

0.0582 / 0.0895 => 0.650 mol/kg

hope this helps!

Answer 2

let suppose we have 100g sample solution:
10.5% by mass, there is 10.5g glucose.
89.5g is water.
Molality = moles of solute / kilograms of solvent
no of moles= 10.5g glucose/ molar mass (180g)
= 0.058moles
0.058mole glucose / 0.089kilograms of water
=0.65molal
=hope it helps