Question

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?

Answer 1

Answer:

The molecular formula of the compound is C6H6

Explanation:

Step 1: Data given

Assume the mas = 100 grams

The compound contains:

92.3 % C = 92.3 grams C

7.7 % H = 7.7 grams

Step 2: Calculate moles

Moles = mass / molar mass

Moles C = 92.3 grams / 12.01 g/mol

Moles C = 7.685 moles

Moles H = 7.7 grams / 1.01 g/mol

Moles H = 7.62 moles

Step 3: Calculate mol ratio

We divide by the smallest amount of moles

C: 7.685 /7.62 = 1

H: 7.62 / 7.62 = 1

The empirical formula = CH

This formula has a molecular mass of 13.02 g/mol

Step 4: Calculate molecular mass

Molar mass = mass / moles

Molar mass = 11.08 grams / 0.142 moles

Molar mass = 78.02 g/mol

Step  5: Calculate molecular formula

For the molecular formula, we need the molecular weight:

78.02 / 13.02 = 6

We have to multiply the empirical formula by 6

6*CH = C6H6

The molecular formula of the compound is C6H6