Answer:
The molar mass of the organic solid is 119.9g/mol.
The molecular formula of an organic solid is C4H8O4
Step-by-step explanation:
Step 1
We find the Molar mass
From the above question, we are given:
A solution of 0.650 g of the solid in 27.8 g of the solvent diphenyl gave a freezing point depression of 1.56 °C. Calculate the molar mass and determine the molecular formula of the solid (kf for diphenyl is 8.00 °C/m)
A freezing point depression = 1.56 °C.
Mass of organic solid= 0.650 g
Mass of diphenyl = 27.8 g
Converting to kilograms
1000g = 1kg
27.8g =
Cross Multiply
= 27.8g × 1 kg/1000g
= 0.0278kg
Boiling point constant = 8.00 °C/m
Molar mass of the organic compound = Boiling point constant × Mass of solid /Freezing point depression × Mass of diphenyl
Molar mass of the organic compound =
8.00 °C/m × 0.650g/1.56°C × 0.0278kg
= 5.2 g°C/m ÷ 0.043368 g°C
= 119.9040767 g/mol
Approximately = 119.9 g/mol
Step 2
Find the Molecular formula
Molecular formula = CxHyOz
Let x = Carbon, y = Hydrogen, z = Oxygen
For x = Carbon
Atomic mass of Carbon = 12.01078
x = % of Carbon in the compound × Molar mass of the organic compound/atomic mass of Carbon
x = 40% × 119.9 g/mol / (12.01078
x = 3.99
x = Approximately = 4
For y = Hydrogen
Atomic mass of Hydrogen = 1.007947
y = % of Hydrogen in the compound × Molar mass of the organic compound/Atomic mass of Hydrogen
x = 6.7% × 119.9 g/mol) / 1. 007947
x = 7.97
x is Approximately = 8
For z = Oxygen
Atomic mass of Oxygen = 15.99943
z = % of Oxygen in the compound × Molar mass of the organic compound/Atomic mass of Oxygen
z = 53.3% × 119.9 g/mol /15.99943
z = 3.99
z is approximately ≈ 4
Therefore,
The molar mass of the organic solid is 119.9 g/mol.
The molecular formula of an organic solid is C4H8O4