Question

What would be the boiling point of a 3.60 mole aqueous sucrose solution? The boiling point elevation constant for water is 0.512 degrees Celsius per mole.

A) 98.16 degrees Celsius
B) 101.8 degrees Celsius
C) 107.0 degrees Celsius
D) 108.1 degrees Celsius

I've tried so hard to figure this out, but I just don't understand it :( Can anyone help me please?

Answer 1

i am guessing you meant "3.60 molal". this is a solution concentration expressed in molality (not molarity or mole).

Answer 2

let's go out on a limb. the answer is B. give me some time to type the explanation.

Answer 3

so the boiling point elevation should be about 1.8 degrees. and here is why:

Answer 4

boiling point elevation (in degrees) = (boiling point elevation constant) * (*molal* concentration)

Answer 5

So boiling point elevation = 0.512 * 3.60 = 1.84 degrees

new boiling point = 100.0 deg Celsius + 1.84 degrees = 101.8 degrees Celsius and choice B should be the correct answer.

note: the solute concentration is 3.60 molal (identical to the sucrose concentration) because sucrose does not usually dissociate like NaCl (or fall apart in some chemical reaction).