Question

A compound has a molecular weight of 112.124 atomic mass units and the empirical formula C3H4O. What is the molecular formula of the compound?
A.C₂H₂O
B. C9H12O3
C. C8H4O₂
D. C4H8O₂
E.C6H8O₂

Answer 1

Answer:

$\fbox{ The correct molecular formula of the compound is E. C6H8O2.}$

Explanation:

The most straightforward whole number ratio between the atoms of each component in a compound is represented by its empirical formula. The molecular weight of each element in the compound, or in this example, its percentage composition, is utilized to get the empirical formula, which is "C3H4O."

First, let's calculate the molar mass of the empirical formula C3H4O.

$C_3H_4O = 36.03 + 4.04 + 16.00 = 56.07 \: g/mol$

Now, let's calculate the molar mass of each option:

$A. \: C_2H_2O = 24.02 + 2.02 + 16.00 = 42.04 \: g/mol$

$B. \: C_9H_{12}O_3 = 108.09 + 12.12 + 48.00 = 168.21 \: g/mol$

$C. \: C_8H_4O_2 = 96.08 + 4.04 + 32.00 = 132.12 \: g/mol$

$D. \: C_4H_8O_2 = 48.04 + 8.08 + 32.00 = 88.12 \: g/mol$

$E. \: C_6H_8O_2 = 72.06 + 8.08 + 32.00 = 112.14 \: g/mol$

Hence, Option E is the correct answer.

Alternate Method:

To find the molecular formula, we can divide the molecular weight of the compound by the molar mass of the empirical formula to get the "n" value, which is the factor by which the empirical formula is multiplied to get the molecular formula.

Molecular Formula = n × (Empirical Formula)

Using the molecular weight and the molar mass of the empirical formula, we find:

n = Molecular Weight / Molar Mass of Empirical Formula

n = 112.124 / 56.07 ≈ 2

Now, we have to multiply the empirical formula by 2 to find the molecular formula.

Molecular Formula = (C3H4O) × 2 = C6H8O2

Hence, the correct molecular formula of the compound is E. C6H8O2.

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