Question

To determine the freezing point depression of a LiCl solution, Toni adds 0.317 g of LiCl to the sample test tube along with 20.5 mL of distilled water. Determine the concentration, in molality, of the resulting solution. MW of LiCl is 42.394 g/mol Density of H2O is 0.9982 g/mL

Answer 1

0.365 m

Step-by-step explanation:

The definition of molality is:

• molality = moles of solute / kg of solvent

First we calculate the moles of the solute, LiCl. We do so using its molar mass:

• 0.317 g ÷ 42.394 g/mol = 7.48x10⁻³ mol

Then we calculate the mass of the solvent, water. We do so using its density:

• 20.5 mL * 0.9982 g/mL = 20.5 g

• 20.5 g / 1000 = 0.0205 kg

Finally we calculate the molality of the solution:

• 7.48x10⁻³ mol / 0.0205 kg = 0.365 m