Answer:
The molecular formula of the compound is: C14H12O4
Explanation:
Step 1: find molality
ΔT = Kf x m
ΔT = Tfinal - Tinitial = 3.37 - 5.50 = -2.13
molality (m) = ΔT/Kf = -2.13/-5.12 = 0.416 m
step 2: find number of moles
m = number of moles (n)/Kg solvent which is the benzene
n = molality x Kg solvent = 0.416 molality X (10 x 10^-3 Kg) = 0.00416 mole
Step 3: find molecular mass of the organic compound
n = mass/Molecular mass = m/Mm
Mm = m/n = 1.02/0.00416 = 245.19 g/mole of organic compound molecular formula
Step 4: find number of mole of each compound
let consider it being in 100g where each % will correspond to the mass of the element in 100g of the compound.
C = mass/molar mass = 68.85/12.01 = 5.7327 mole
H = mass/molar mass = 4.9/1.01 = 4.8515 mole
O = mass/molar mass = 26.2/16 = 1.6375 mole
Step 5: divide by smallest number of mole
C = 5.7327/1.6375 = 3.5 = 7/2
H = 4.8515/1.6375 = 3
O = 1.6375/1.6375 = 1
C7/2H3O1
multiply by two to remove the fraction: C7H6O2 in which the empirical molecular mass = 122.13 g/mole
to find the factor for the molecular formula x = Mm of molecular/Mm of empirical = 245.19/122.13 = 2
Multiply the empirical by 2 = 2 x (C7H6O2) = C14H12O4
