Question

HELP! >__< seems like an impossible problem...

If you make a solution from 100.0g of unknown solute and 1000mL of water and find that it's boiling point is 1.024 degree C higher then that of pure water, what can you conclude about it's molecular weight?

so.. Kbp for water is 0.512

Answer 1

this is a colligative property question, boiling point elevation, in which amount of solute added affects the temperature at which the solvent will boil at due to obstruction of the solvent particles by the solute as they try to escape the liquid phase and evaporate.

use: \[\Delta T = imK _{bp}\]

i = van't hoff factor
m=molality

Answer 2

remember that molality= moles of solute/ Kg of solvent

and moles=mass/molecular weight

so the equation you're left with is

\[\Delta T = i (mass/MW/Kg solvent) K _{bp}\]

use some algebra and isolate MW