What is the molality??

Question

What is the molality of the solution formed by dissolving 0.64 g of para-dichlorobenzene in 10 mL of cyclohexane? The density of cyclohexane is 0.779 g/mL

Answer 1

first find moles using molar mass:

0.64 grams para-dichlorobenzene @ 147.00 g/mol = 0.00435 moles

since molality is the moles of solute per kilogram of solvent:

10ml cyclohexane @ 0.779 g/ml = 7.79 grams of solvent

& molality :

0.00435 moles solute / 0.00779 kilograms solvent = 0.559 Molal

your answer is: 0.56 molal  (2sigfigs)