Understand Molar Mass: Find out the molar mass of the empirical formula by summing the atomic masses of all the elements present.

Analyze Elemental Composition: Determine the empirical formula's elemental composition as a percentage.

Calculate Molecular Weight: Acquire information about the molecular weight (or molar mass) of the compound. This is usually provided experimentally through techniques such as mass spectrometry.

Calculate Multiplier: Divide the molecular weight by the empirical formula's molar mass. The result is a whole number, which is the multiplier (n).

Multiply Subscripts: Multiply all subscripts in the empirical formula by n to obtain the molecular formula.

Verify the Molecular Weight: Verify that the molecular weight of the molecular formula matches the experimentally obtained molecular weight.

Here's an example using ethylene glycol to illustrate these steps:

Empirical formula: CH₂O

Molar mass of empirical formula (CH₂O):

(1 x 12.01 g/mol C) + (2 x 1.01 g/mol H) + (1 x 16.00 g/mol O) = 30.03 g/mol

Experimental molecular weight of ethylene glycol: 62.07 g/mol

Multiplier (n):

62.07 g/mol / 30.03 g/mol = 2

Molecular formula:

C₂H₄O₂

Molecular weight of molecular formula (C₂H₄O₂):

(2 x 12.01 g/mol C) + (4 x 1.01 g/mol H) + (2 x 16.00 g/mol O) = 62.07 g/mol

Thus, the molecular formula for ethylene glycol is C₂H₄O₂, which matches the experimental molecular weight.