Question

11) A pure sample of a hydrocarbon (a compound that contains only hydrogen and

carbon is found to be 74.5 % carbon by mass.
Find the empirical formula for the compound.
6. If the molar mass of the compound is 16 05 g/mol, find its molecular
formula.

Answer 1

EMPIRICAL FORMULA IS CH4

MOLECULAR FORMULA IS CH4

Step-by-step explanation:

Carbon percentage by mass = 74.5 %

Hydrogen = 100 % - 74.5 % = 25.5 %

To calculate the empirical formula, we follow these steps:

Write out the percentage composition and divide by the relative atomic mass of the constituent elements

Carbon = 74.5 % / 12 = 6.2083

Hydrogen = 25.5 % / 1 = 25.5

Then, divide the values obtained by the smaller value:

Carbon = 6.2083 / 6.2083 = 1

Hydrogen = 25.5 / 6.2083 = 4.107

Then, round up the values too a whole number:

Carbon = 1

Hydrogen = 4

The empirical formula hence is C H4

Calculating the molecular formula:

(CH4) n = molar mass

(CH4)n = 16.05

(12 + 1*4) n = 16.05

(16)n = 16.05

n = 16.05 / 16

n = 1.003

The molecular formula is (CH4)

In conclusion, the empirical formula is CH4 and the molecular formula is also CH4