When 19g of a certain molecular compound X are dissolved in of benzonitrile , the freezing point of the solution is measured to be . Calculate the molar mass of X.

The given question is incomplete. The complete question is:

When 19 mg of a certain molecular compound X are dissolved in 200 g of benzonitrile , the freezing point of the solution is measured to be . Calculate the molar mass of X. Freezing point of pure benzonitrile =

Molar mass of X is 1271 grams

Explanation:

Depression in freezing point =

Mass of solute (X) = 19 g

Mass of solvent (benzonitrile) = 200.0 g = 0.2 kg (1 kg = 1000 g)

Formula used :  

where,

= change in freezing point =

i = Van't Hoff factor = 1

= freezing point constant = 5.35 K.kg/mole

m = molality

Now put all the given values in this formula, we get

Thus molar mass of X is 1271 grams

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.