Answer:
Molecular formula of ethylene glycol is C₂H₆O₂.
Explanation:
Given data:
mass of ethylene glycol = 23.4 mg
mass of water = 20.42 mg
mass of carbon dioxide = 33.27 mg
molar mass of ethylene glycol = 62.0 g / mol
Molecular formula of ethylene glycol = ?
Solution:
percentage of carbon = (33.27 mg/ 23.46 mg) × (12 /44) × 100
= (1.4182× 0.27) × 100 = 38.29
percentage of hydrogen = (20.42 mg/ 23.46 mg) × (2 /18) × 100
= (0.8704× 0.11) × 100 = 9.67
percentage of oxygen = 100 - (38.29 + 9.67 )
= 100 - 47.96 = 52.04
Now we will determine the number of grams atoms of carbon, hydrogen and oxygen.
No. of gram atoms of carbon = 38.29 /12 = 3.19
No. of gram atoms of hydrogen = 9.67 / 1 = 9.67
No. of gram atoms of oxygen = 52.04 / 16 = 3.25
Atomic ratio:
C :H :O 3.19/ 3.19 : 9.67 / 3.19 : 3.25 /3.19
C :H :O 1 : 3 : 1
Molecular formula:
Molecular formula = n × (empirical formula)
n = molar mass of compound / empirical formula mass
empirical formula mass= 1 × 12 + 3 × 1 + 1 × 16
empirical formula mass= 12+3 +16 = 31
n = 62 g /mol / 31 = 2
Molecular formula = n × (empirical formula)
Molecular formula = 2 × (CH₃O)
Molecular formula = C₂H₆O₂
