elemental analysis indicates the simplest formula of an unknown is C2H4O. when 0.775g of the compound is dissolved in 50g of benzene(C6H6), the solution freezes at 5.06 degree C. what are the molecular weight and the molecular formula of the compound? the freezing point of pure benzene is 5048 degree C, and its Kf is 5.12 degree C/m.
delta Tf= 5.48C-5.06C=0.42C
m=0.42C/(5.12C/m )=0.082m C6H6
(0.082mol/kg) * (50g/1000g) = 4.1E-3 mol compound
0.775g/4.1E-3 = 189g/mol compound
n=(189g/mol) / (44 g/mol) ~ 4
4* (C2H4O) = C8H16O4
** i would like to know is the problem solved correctly.
I don't like to see 4.3 rounded to 4 but I don't see anything wrong with your work. It look fine to me.
3 answers