Calculation of Molecular Formulas

What is the Molecular Formula?

The molecular formula represents the actual formula of a compound and gives the composition of the molecule

The Empirical Formulas vs the Molecular Formulas

Steps for Determining the Molecular Formula

1) Find the empirical formula

1) n= molecular molar mass empirical formula mass

2) n x empirical formula= molecular formula

Exercises

1. Calculate the molecular formula of a compound with the empirical formula CH₂O and a molar mass of 150 g/mol.

2. Acetylene gas is 92.3 % carbon and 7.7 % hydrogen (by mass), and its molar mass is 26 g/mol. What is its molecular formula?

3. The empirical formula of a compound is known to be CH₂, and its molar mass is 56 g/mol. What is its molecular formula?

4. A compound contains 12.8% C, 2.1 % H, and 85.1 % Br (by mass). Calculate the empirical formula and the molecular formula of this compound given the molar mass is 188 g/mol.

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