Question

Calculate the theoretical freezing point depression of 8.02g of .5 mol CH4 dissolved in 50 mL of deionized water?

Answer 1

The freezing point depression is defined as the freezing point of pure solvent ( [equal to in water) minus the freezing point of the solution ().

Because , is positive.

On the other hand, is proportional to the concentration of the solution (m) hence

where

= the number of celsius degrees that frezing point is lowered

= a constant characteristic of the solvent [for water

= Molality of the solution ( )

in the problem we has 8,02 g of in 50 mL of .

Mol of is:

and density of water at is 0,998 g/L approximately 1,0 g/L hence 50mL of water is equal at of water.

and molalilty is:

Thus,

as the freezing point of water is the theorical freezing point depression of 0,5 mol the CH4 is -18 (.)