Question

Find the molality of the solution if 42 grams of lithium chloride (LiCl) are dissolved in 3.6 kg of water.

Answer 1

The molality is calculated using the following rule:
molality = number of moles of solute / kg of solvent

From the periodic table:
molar mass of lithium = 6.941 gm
molar mass of chlorine = 35.453 gm

molar mass of LiCl = 6.941 + 35.453 = 42.394 gm
number of moles found in 42 gm = mass / molar mass = 42 / 42.394 = 0.99

molality = 0.99 / 3.6 = 0.275 m