delta T = Kb*molality
Calculate molality
molality = moles/kg solvent.
Calculate moles.
moles = grams/molar mass
Calculate molar mass. This usually is an approximate molar mass.
The first part of the problem is to determine the empirical formula.Take a 100 g sample, which will give you
51.44 g C
2.88 g H
45.68 g O.
Convert each of the grams above to moles. moles = grams/atomic mass.
Now determine the ratio of the elements to each other. The easy way to do that is to divide the smallest number by itself which assures you of getting 1.000 for that element. Then divide the other numbers by the same small number and round to a whole number. (Don't round too much; i.e., if you have a number with a half, for example 2.5, that could become a whole number at 5.0)
Trimellitic acid containing carbon, hydrogen, and oxygen has 51.44% C, 2.88% H, and 45.68% O. It can be obtained by oxidation of coal with nitric acid. A 2.416-g sample of this compound was dissolved in 40.00 g of acetone, producing a solution that boils at 56.64°C. Kb for acetone is 1.71°C/molal. Pure acetone has a boiling point of 56.20°C.
What is the molecular formula for the compound?
a. C2HO
b. C3H2O2
c. C6H4O4
d. C9H6O6
e. C10H7O7
1 answer
1 answer