Question

1. A 2.00 g sample of a particular compound was dissolved in 15.0 g of carbon tetrachloride. The boiling point of this solution was determined to be 77.85ºC.

For pure CCl4, TB = 76.50ºC and KB = 5.03°C·kg/mol

Calculate the boiling point elevation, ΔTB, for this solution.

2.Use the KB given in the problem information above and the boiling point elevation calculated in problem 1, calculate the molality of this solution (in mol solute/kg solvent)

3.Calculate the mass of the solvent (CCl4) in kg.

4.Use the molality calculated in question 2 and the solvent mass calculated in question 3 to determine the number of moles of solute present in this solution.

Answer 1

I don't believe you didn't know how to do any of this.
1. delta Tb = impure b.p.- pure b.p.

2. delta T = Kb*m
Substitute and solve for m.

3. Isn't the mass given in the problem. Convert to kg.

4. m = mols/kg solvent.
You know m and kg solvent, solve for mols