Question

An aqueous solution freezes at -3.47⁰C. What is its boiling point? Show all calculations leading to an answer.

Answer 1

what are the formulas for freezing point depression and boiling point elevation?

Answer 2

freezing point depression is ΔT = iK f m
boiling point elevation is ΔTb = Kbm

Answer 3

Okay, so use the first one to find molality, m

then use that value in the second equation

Answer 4

how do I find molality? sorry I'm very confused

Answer 5

In the first formula you posted (freezing point depression), plug the values in for \(\Delta T\) is given in the question, you know \(K_f\) because it's a constant.

assume that i is 1

Answer 6

ok so -3.47 C = (1)(1.86)(m)
is this correct so far?

Answer 7

yep that's right

Answer 8

ok so -3.47 / 1.86 = -2.38
yes?
whats after that

Answer 9

-1.86 should be negative, so you end up with a positive value

m=2.38

now use this value in the second equation (with the constant Kb)

Answer 10

ok so 0.512 x 2.38 = 1.22
is this right?

Answer 11

yep, that's the change in temperature from the normal boiling point of water

that's not the final answer though, re-read the question

Answer 12

so how do I find the boiling point mentioned in the question? do I add it to the freezing point?

Answer 13

nope, you add it to the normal boiling point of water

Answer 14

so 1.22 + 100 = 101.22?

Answer 15

yep

Answer 16

Thats it? Thank you so much for your help :)

Answer 17

yes, thats the answer. no problem !