The empirical formula provides the proportions of the elements present in a compound, but not the actual numbers or arrangement of atoms. On the other hand, the molecular formula provides the number of atoms of each of the elements present in one molecule of a specific compound. Keep reading to learn how to calculate them!
Calculation of an Empirical Formula:
Obtain the mass of each element in grams.
Convert the mass of each element to moles by using the molar mass from the periodic table.
Divide each mole value by the smallest number of moles calculated.
Round the value to the nearest whole number.
(To convert the mass to moles for a single element, multiply its atomic weight by the molar mass constant (1 g/mol)).
Example:
Calculation of a Molecular Formula:
Calculate the empirical formula.
Divide the molar mass of the compound by the empirical formula mass.
Multiply each of the subscripts within the empirical formula by the whole number calculated in #2.
Example:
I hope you'll be able to apply these formulas in your chemistry related classes or hobbies!
Written by: Ashlee Liu
References:
“Steps for Determining an Empirical Formula.”Chem Tamu, 2018, www.chem.tamu.edu/class/fyp/stone/tutorialnotefiles/fundamentals/empirical.htm.
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