Not only can the freezing point or boiling point of a solution be determined as in the previous example, but the molecular mass of a compound can be obtained by observing a freezing point or boiling point of a solution.

For example...5.0 g of a white solid is added to 50.0 g H₂O. The boiling point of the solution is 100.3 °C. If i = 1 what is the molecular mass of the solid, K_b for water is 0.51 °C•kg•mol^-1?

The change in the boiling point is related to m , and m is concentration in mol per kg of solvent. So, the change in temperature is related to the number of moles of material dissolved. The number of moles of material dissolved can be determined!

Now, we know that 0.0275 mol of the material weighs 5.0 g. 

since the temperature change, 0.3 °C, has just one significant figure our answer should have just one significant figure!