GC boiling point elevation problem

[ems5184]

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This is from TopScore #1, I think their answer is wrong, could somoene work this one out and see what they get please.

If the Kb of a solvent is 3.51 degrees C/m, and the boiling point of the pure solvent is 70.4 degrees C, then what is the boiling point of a 4m solution of solute dissolved in the solvent?

A. 70.4
B. 84.4
C. 98.5
D. 112.5
E. None of these

The answer key says C, but I keep getting B.

 

[drat]

Yeah, I get the same as you, B.

 

[BAJackson16]

thats weird ,
my answer key says B

 

[ems5184]

Yea, I was pretty sure the answer was B, I guess for some reason my answer key was a little different, oh well. Thanks for checking me guys.

 

[jk5177]

I work through the problem, and I also got B. HOWEVER, I can see why it would be. It would be C, IF THE SOLUTE DISSOCIATE. THAT MAKES SENSE BECAUSE IT IS COLLIGATIVE PROPERTIES. SO A MOLECULE THAT DISSOCIATES ACTUALY COUNTS AS TWO. The adjustment for this is calle the Van Hoft's Factor.

So, the equation really ought to be

delta t = (van hoft factor) (Kb) (molality)


In my experience with Top Score, most of their answers are really legit. I don't remember them have wrong answers.

Hope this helps.

 

[drat]

I work through the problem, and I also got B. HOWEVER, I can see why it would be. It would be C, IF THE SOLUTE DISSOCIATE. THAT MAKES SENSE BECAUSE IT IS COLLIGATIVE PROPERTIES. SO A MOLECULE THAT DISSOCIATES ACTUALY COUNTS AS TWO. The adjustment for this is calle the Van Hoft's Factor.

So, the equation really ought to be

delta t = (van hoft factor) (Kb) (molality)


In my experience with Top Score, most of their answers are really legit. I don't remember them have wrong answers.

Hope this helps.

This is exactly right...Did the question specify a salt?

But someone mentioned their Topscore had B as the correct answer???