Empirical Formula from Analysis



The procedure is shown below:

Example: Hg reacts with Cl forming a compound that is 73.9 % Hg and 26.1% Cl by mass.

Question 1: What is the empirical formula of the compound? (Note: Atomic weights of Hg and Cl are 200.6 and 35.5, respectively).

Hence, the empirical formula is HgCl2

Question 2: What is the relation between: a "Molecular Formula" and an "Empirical Formula"?

Remember the following:
To find the empirical formula of the molecular formula, C6H12O6, we need to divide by the common number, which is 6 in this example, and we obain: CH2O

So, a molecular formula is an actual formula of the molecule, and the empirical formula is a simpler (abstracted) form.
Similarly, 180 g/mol (molecular formula weight), and then dividing it by 6 (the common number), we obtain 30 g/mol (empirical formula weight).

Hence, knowing the empirical formula, its weight and the molecular formula weight will let us determine the molecular formula.

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Date of last modification: Summer , 2019