A compound that is composed of carbon, hydrogen, and oxygen contains 70.6% C, 5.9% H, and 23.5% O by mass. The molecular weight

Question

2 months ago

6

of the compound is 136 amu. What is the molecular formula? A) B) C) D) E)
A) c8 H8 O2
B)C8 H4 O
C)C4 H4 O
D)C9 H12 O

1 answer:

Tems11 [2.7K] · Answer 1 · 2026-03-20T01:03:03+03:00

Answer: The molecular formula will be $C_8H_8O_2$

Explanation:

When percentages are provided, we assume the total mass to be 100 grams.

Thus, the mass of each element corresponds to the specified percentage.

Mass of C= 70.6 g

Mass of H = 5.9 g

Mass of O = 23.5 g

Step 1: convert given masses to moles.

Moles of C = $\frac{\text{ given mass of C}}{\text{ molar mass of C}}= \frac{70.6g}{12g/mole}=5.9moles$

Moles of H = $\frac{\text{ given mass of H}}{\text{ molar mass of H}}= \frac{5.9g}{1g/mole}=5.9moles$

Moles of O = $\frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{23.5g}{16g/mole}=1.5moles$

Step 2: For determining the mole ratio, divide each molar amount by the smallest number of moles calculated.

For C = $\frac{5.9}{1.5}=4$

For H = $\frac{5.9}{1.5}=4$

For O = $\frac{1.5}{1.5}=1$

The resulting ratio of C: H: O= 4: 4: 1

Hence, the empirical formula obtained is $C_4H_4O$

The empirical weight is calculated as $C_4H_4O$ = 4(12)+4(1)+1(16)= 68g.

The molecular weight = 136 g/mole

Now the molecular formula needs to be obtained.

$n=\frac{\text{Molecular weight }}{\text{Equivalent weight}}=\frac{136}{68}=2$

The molecular formula can be derived as= $2\times C_4H_4O=C_8H_8O_2$