Question

The molality of a solution that is prepared by dissolving 64.2 mL of methanol (d = 0.791 g/mL, MM = 32 g/mol) in 137.6 g ethanol is ______ m. Report your answer with three significant figures. Do not include units.

Answer 1

The molality is 11.5

Step-by-step explanation:

Molality of solution = number of moles of methanol ÷ mass of ethanol in kilograms

Number of moles of methanol = density × volume/MM = 0.791×64.2/32 = 1.587 moles

Mass of ethanol = 137.6 g = 137.6/1000 = 0.1376 kg

Molality of solution = 1.587 ÷ 0.1376 = 11.5 (to 3 significant figures)