A molecular compound contains 92.3 % carbon and 7.7 % hydrogen by mass.If 0.142 mol of the compound weighs 11.08 g,what is its molecular formula? A)C₈H₈ B)C₈H₁₀ C)C₄H₈ D)C₆H₆ E)CH

Question

Quizplus · Accepted Answer

1) Calculate the mass of 0.142 mol of the compound:
11.08 g / 0.142 mol = 77.97 g/mol

2) Determine the empirical formula of the compound:
Assuming we have 100 g of the compound, we have:
- 92.3 g carbon
- 7.7 g hydrogen

Converting these to moles:
- 92.3 g carbon / 12.01 g/mol = 7.686 mol carbon
- 7.7 g hydrogen / 1.01 g/mol = 7.623 mol hydrogen

Dividing by the smallest number of moles (7.623), we get a ratio of approximately 1:1.
Therefore, the empirical formula is CH.

3) Calculate the molecular formula:
From the empirical formula, we know that the molecular formula is some multiple of CH.
Let's assume the molecular formula is (CH)n, where n is the number of CH units.
The molecular mass is:
n x (12.01 g/mol + 1.01 g/mol) = n x 13.02 g/mol

We know that the molecular mass is 77.97 g/mol, so we can set up the following equation:
n x 13.02 g/mol = 77.97 g/mol

Solving for n:
n = 5.99

The molecular formula is therefore:

CH x 6 = C6H6

Which is option D.

A Molecular Compound Contains 92