Empirical vs Molecular Formulas
Molecular formula: represent the actual numbers of atoms of the different
elements in one molecule of a compound.
An example
An example
glucose has a molecular formula of C6H12O6
water has a molecular formula of H2O
Empirical formula: is the simplest whole numbers non-reducible ratio formula for a
molecular formula or compound.
An example
glucose has an empirical formula of C1H2O1
An example
water has an empirical formula of H2O
Sooooo SOMETIMES empirical formulas are also molecular formulas
The empirical formula for hydrogen peroxide is HO whereas the “molecular formula” is H2O2.
What is the lowest ratio of the subscripts in HO?________
What is the lowest ratio of the subscripts in H2O2? _______
What is the empirical formula mass of HO?_______
What is the molar mass of H2O2? ________
How does the ‘empirical formulas mass” compare to the “molecular formula molar mass”?
____________________________________________________
The empirical formula for acetylene gas is CH whereas the “molecular formula” is C2H2.
What is the lowest ratio of the subscripts in CH?________
What is the lowest ratio of the subscripts in C2H2? _______
What is the empirical formula mass of CH?_______g/mol
What is the molar mass of C2H2? ________g/mol
How does the ‘empirical formula’s mass” compare to the “molecular formula’s molar
mass”?_____________________________________________________
The empirical formula for cyclohexane is CH whereas the “molecular formula” is
C6 H 6 .
What is the lowest ratio of the subscripts in CH?________
What is the lowest ratio of the subscripts in C6H6? _______
What is the empirical formula mass of CH?_______g/mol
What is the molar mass of C6H6? ________g/mol
How does the ‘empirical formula’s mass” compare to the “molecular formula’s molar
mass”?_____________________________________________________
The empirical formula for eugenol (active component in cloves) is C5H6O whereas the “molecular
formula” is C10H12O2.
What is the lowest ratio of the subscripts in C5H6O?________
What is the lowest ratio of the subscripts in C10H12O2? _______
What is the empirical formula mass of C5H6O?_______g/mol
What is the molar mass of C10H12O2? ________g/mol
How does the ‘empirical formula’s mass” compare to the “molecular formula’s molar mass”?
_____________________________________________________
Finding a MOLECULAR FORMULA via the empirical formula and molar mass
Canthaxanthin is the molecule responsible for the color of the American flamingo. It’s empirical
formula is C20H25O. The molar mass of canthaxanthin is 562g/mol.
What is the molecular formula of canthaxanthin? ________________
Caffeine found in coffee and tea has an empirical formula of C4H5ON2. The molar mass of
caffeine is 194 g/mol. What is the molecular formula for caffeine?_________________
Ethylene glycol ( antifreeze) has an empirical formula of CH3O. The molar mass of ethylene glycol
is 62 g/mol. What is the molecular formula of ethylene glycol?_____________________
Ammonia has an empirical formula of NH3. The molar mass of ammonia is 17 g/mol. What is the
molecular formula of ammonia?_______
Aspartame ( a sweetener) has an empirical formula of C14H18O5N2. The molar mass of aspartame
is 294 g/mol. What is the molecular formula of aspartame?_______________
Gylceraldehyde has an empirical formula of CH3O and a molar mass of 93 g/mol. What is the
molecular formula of gylceraldehyde?____________________
Tartaric acid ( added to food to achieve a sour taste) has an empirical formula of C 2H3O3 and a
molar mass of 150 g/mol. What is it’s molecular formula/_________________
SUBSCRIPTS in a FORMULA can be represented as MOLES
Ex: C6H12O6 refers to 6 moles C, and 12 moles H, and 6 moles O related to
ONE mole C6H12O6
Sooo Given CxHyOz , IF the x, y, and z info in moles can be calculated, then an
empirical formula can be determined