[Konsy]

 Hi  I'm a new member I'm not sure how this works but i have a prelab and I'm not sure if my answer is right so it would be awesome if someone could tell me whether my solution is correct or not

A compound containing only boron, nitrogen and hydrogen was found to be 40.3% B, 52.2% N, and 7.5% H by mass. If 3.301g of this compound is produced freezes at 1.30ºC. If Kg for benzene is 5.12ºC/m and the freezing point of pure benzene is 5.48ºC, What is the molecular weight of this compound?

deltaTf = KfXm

(5.48ºC-1.30ºC) = 5.12ºC/m x m

m= 4.18ºC / 5.12ºC/m
m= 0.816

m= mole of solute(unknown) / kg Solvent(benzene)

mole solute= 0.816x0.05kg
mole of solute= 0.0408 mole

molar mass= g solute / mole solute
molar mass= 12.00g/0.0408 mole
molar mass= 294.12g/mole

[Yggdrasil]

The procedure for solving for molecular weight looks right, but in the question I don't see anything about the volume/mass of benzene used or how much of the compound was dissolved in the benzene.

[champ]

may u please tell me that from where did u get 12.oog??