Gchem Question!!

[akeurogh]

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Okay this question is kind of weird.

A nonelectrolyte sample of 45g is placed into 250g of water. Under a pressure of 1 atm, the boiling point of the solutions is 100.52 C. What is the molecular weight of the nonelectrolyte in g/mol? (Kb of H20=0.52 C kg/mol)


I understood they got the answer. But they say that the boiling point elevation is one times the boiling point elevation constant (Kb), thats how they derive the answer. But why is that?


thanks for the help!!🙂

 

[UCB05]

Okay this question is kind of weird.

A nonelectrolyte sample of 45g is placed into 250g of water. Under a pressure of 1 atm, the boiling point of the solutions is 100.52 C. What is the molecular weight of the nonelectrolyte in g/mol? (Kb of H20=0.52 C kg/mol)


I understood they got the answer. But they say that the boiling point elevation is one times the boiling point elevation constant (Kb), thats how they derive the answer. But why is that?


thanks for the help!!🙂

The question assumes you know the boiling point of water is 100C at 1atm. Knowing that, you can see that the boiling point of the solution has been elevated .52C. The equation for BPE = m(Kb). BPE=.52, Kb=.52, therefore m=1mol/kg.
m=1mol/kg = x/.250kg H2)
x=.25mol
mm = g/mol = 45/.25 = 180g/mol

 

[akeurogh]

ohhh yeahhh!!!! thanks a lot!