Question

What is the motility of a solution labeled "8.6% glucose (C6H12O6) by weight? ( note: if the question does not give the solvent assume its water)

Answer 1

Molality, also called molal concentration, is a measure of the concentration of a solute in a solution in terms of amount of substance in a specified amount of mass of the solvent.

Glucose is the solute & water is the solvent. then the solution = water + glucose
8.6% by weight glucose solution tells you to assume 100g of solution, which is 8.6g of glucose/100g solution
So, just for clarification, if you were given an amount of solution to start with, it would look like this:
100g solution x (8.6g glucose/100g solution) = 8.6g glucose
Since we assumed 100g, we started with 100g.
But you need moles of solute, so its
Moles of solute = 8.6 g glucose x (1 mol glucose/180.16g glucose) = 0.107 moles
Since the solvent is water, and you're assuming 100g of solution:
grams of water = grams of solution - grams of glucose
grams of water = 100g - 8.6g = 91.4g water