Empirical and Molecular Formula Practice
1. A compound contains 18.8% sodium, 29.0% chlorine, and 52.2% oxygen, by mass. If the molar mass
of the compound is 122.44 g/mol, determine the empirical and molecular formulas.
2. A 4.99 gram sample of a compound contains 1.52 grams of nitrogen atoms and 3.47 grams of oxygen
atoms. The molar mass of the compound is between 90.0 g and 95.0 g. Determine the empirical and
molecular formulas. Also, calculate the actual molar mass of this compound.
3. Ascorbic acid is another name for Vitamin C. It is composed of 40.92% carbon, 4.58% hydrogen, and
54.50% oxygen, by mass. Determine the empirical formula for ascorbic acid.
4. H3PO4, Phosphoric acid, is used in detergents, fertilizers, toothpastes and flavoring in carbonated
beverages. Calculate the percent composition by mass to two decimal places of H, P and O in this
compound.
5. What is the percent composition by mass of aspartame (C14H18N2O5), the artificial sweetener
NutraSweet?
6. Ascorbic acid (vitamin C) is 40.92% C, 4.58% H and 54.50% O by mass. What is the empirical
formula of ascorbic acid?
7. What is the empirical formula of each of the following compounds?
a. Talc by mass composition contains 19.2% Mg, 29.6% Si, 42.2% O and 9.0% H.
b. Saccharin has by mass composition 45.89% C, 2.75% H, 7.65% N, 26.20% O and 17.50% S
c. Salicylic Acid, used in aspirin, contains 60.87% C, 4.38% H, and 34.75% O by mass
composition.
d. L-Dopa, a drug used for the treatment of Parkinson’s disease, is 54.82% C, 5.62% H, 7.10% N,
and 32.46% O by mass composition.
8. What is the molecular formula of benzoyl peroxide (the empirical formula is C7H5O2) if the
molecular mass is 242 g/mol?
1. (Answer: Empirical and molecular formula - NaClO4)
2. (Answer: Empirical formula - NO2. Molecular formula - N2O4. Molar mass = 92.04 g/mol)
3 (Answer: Empirical formula - C3H4O3)
4. H: 3.09%, P: 31.61%, O: 65.31%
5. C: 57.14%, H: 6.16%, N: 9.52%, O: 27.18%
6. C3H4O3
7. a.
7b.
Mg3Si4O10H34
C7H5NO3S
7c. C7H6O3
7d. C9H11NO4
8. C14H10O4