A molecule has the empirical formula C4H6O. If its molecular weight is determined to be about 212 g/mol, what is the most likely

Question

andrew11 [14]

3 years ago

8

A molecule has the empirical formula C4H6O. If its molecular weight is determined to be about 212 g/mol, what is the most likely

molecular formula?
a. C12H18O3
b. C8H12O3
c. C11H16O4
d. C4H6O
e. C2H3O

Chemistry

2 answers:

Blababa [14] · Answer 1 · 2022-02-15T20:42:56+03:00

Answer:

The molecular formula is most likely to be first option, $\rm C_{12} H_{18} O_{3}$ .

Explanation:

Both the molecular formula and the empirical formula of a molecule give the types of atoms in that molecule. However, the molecular formula of a molecule gives the exact number of atoms each molecule. On the other hand, the empirical formula gives only a simplified ratio.

For example, if the empirical formula of the molecule is $\rm C_4H_6O$ , then the molecular formula would be $(\rm C_4H_6O)_k$ , or equivalently $\mathrm{C}_{4\, k}\mathrm{H}_{6\, k} \mathrm{O}_{k}$ , where $k$ is a positive whole number ( $1,\, 2,\, \dots$ , etc.) The goal here is to find the value of

Look up the relative atomic mass data on a modern periodic table:

C: 12.011.
H: 1.008.
O: 15.999.

The formula mass of $\rm C_4 H_6 O$ would be

$\begin{aligned}&M(\rm C_4 H_6 O) \cr &\approx 4 \times 12.011 + 6 \times 1.008 + 15.999 \cr &= 70.091\;\rm g \cdot mol^{-1}\end{aligned}$ .

The formula mass of $\mathrm{C}_{4\, k}\mathrm{H}_{6\, k} \mathrm{O}_{k}$ would be

$\begin{aligned}&M(\mathrm{C}_{4\, k}\mathrm{H}_{6\, k} \mathrm{O}_{k}) \cr &\approx (4\, k) \times 12.011 + (6\, k) \times 1.008 + k \times 15.999 \cr &= ( 4 \times 12.011 + 6 \times 1.008 + 15.999)\, k \\ &= (70.091\, k)\;\rm g \cdot mol^{-1}\end{aligned}$ .