Molality is one way of expressing concentration of a substance in a solution. It is moles of the substance per kilogram of the solvent in the solution. So, in order, to determine the molality of the solute benzene in the solution given above, we need to know the moles of benzene and the kilograms of the solvent carbon tetrachloride. We calculate as follows:
Molality = moles benzene / mass of carbon tetrachloride
Molality = 16.2 g benzene ( 1 mol / 78.1 g ) / 282 g CCl4 ( 1 kg / 1000 g)
Molality = 0.7356 mol C6H6 / kg CCl4 or 0.7356 molal
Therefore, the concentration of benzene in this solution is 0.7356 molal.
