Question

Please show all mathematical work. Thank you.

A empty 50 mL flask was weighed and found to be 40.52 grams.

0.8 grams of pyridine was weighed out and added to the 50 mL volumetric flask. It was then diluted to the mark with cyclohexane. The final weight was found to be 79.29 g. With this information find the mole fraction of solute.

Answer 1

mole fraction of solute = moles solute / total number of moles

first calculate the masses of both solute and solvent from the information given.

mass of empty flask = 40.52 g

mass of flask + pyridine + cyclohexane = 79.29 g

mass of pyridine + cyclohexane = 79.29 - 40.52 = 38.77 g

mass of pyridine = 0.8 g

mass of cyclohexane = 38.77 - 0.8 = 37.97 g

moles of pyridine = 0.8 / 79.1 = 0.01

moles of cyclohexane = 37.79 / 84.16 = 0.449

mole fraction of solute = 0.01 / 0.01 + 0.449 = 0.01 / 0.459

mole fraction of solute = 0.022