Problem: Lanthanum(III) chloride dissolves in water according to: LaCl3(s) → La3+(aq) + 3 Cl-(aq). What is the boiling point of the solution when 0.2453 g of LaCl3 (molar mass 245.3 g/mol) is dissolved in 10.0 g of H2O? (Kb of water is 0.512 °C/m.)a. 100.051°Cb. 100.154°Cc. 100.102°Cd. 100.205°Ce. 100.512°C

FREE Expert Solution

We’re being asked to determine the boiling point of a solution. The solution is prepared by dissolving 0.2453 g of LaCl3 in 10 g of water


Recall that the boiling point of a solution is higher than that of the pure solvent and the change in boiling point (ΔT­b) is given by:


Tb=Tb, solution-Tb, pure solvent


The change in boiling point is also related to the molality of the solution:


Tb=iKbm

where: 

i = van’t Hoff factor

m = molality of the solution (in m or mol/kg)

Kb = boiling point elevation constant (in ˚C/m)


Recall that the Molality of a solution is given by:


molality(m)=moles solutekg solvent


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Problem Details

Lanthanum(III) chloride dissolves in water according to: LaCl3(s) → La3+(aq) + 3 Cl-(aq). What is the boiling point of the solution when 0.2453 g of LaCl(molar mass 245.3 g/mol) is dissolved in 10.0 g of H2O? (Kb of water is 0.512 °C/m.)

a. 100.051°C
b. 100.154°C
c. 100.102°C
d. 100.205°C
e. 100.512°C

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Boiling Point Elevation concept. If you need more Boiling Point Elevation practice, you can also practice Boiling Point Elevation practice problems.