Question

A student dissolves 7.9 g of stilbene (C14H12) in 475. mL of a solvent with a density of 1.03 g/mL. The student notices that the volume of the solvent does not change when the stilbene dissolves in it. Calculate the molarity and morality of the students solution. Round both of your answers to 2 significant digits.

Answer 1

Molarity: 0.092M

Molality: 0.090m

Step-by-step explanation:

Molarity, M, is defined as the moles of solute (In this case, C14H12 -Molar mass: 180.25g/mol-) in 1L of solution.

The molality, m, are moles of solute per kg of solvent.

Molarity:

Moles solute:

7.9g * (1mol/180.25g) = 0.04383 moles

Liters solution:

475mL = 0.475L

Molarity: 0.04383 moles / 0.475L = 0.092M

Molality:

kg solvent:

475mL * (1.03g/mL) = 489.25g = 0.48925kg

Molality:

0.04383 moles / 0.48925kg = 0.090m