Practice Problems: Chemical Formulas (Answer Key)
- 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.
H: 3.09%, P: 31.61%, O: 65.31%
- What is the percent composition by mass of aspartame (C14H18N2O5), the artificial sweetener NutraSweet?
C: 57.14%, H: 6.12%, N: 9.52%, O: 27.21%
- 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?
C3H4O3
- 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. Mg3Si4O10H34
b. Saccharin has by mass composition 45.89% C, 2.75% H, 7.65% N, 26.20% O
and 17.50% S. C7H5NO3S
c. Salicylic Acid, used in aspirin, contains 60.87% C, 4.38% H, and 34.75%
O by mass composition. C7H6O3
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. C9H11NO4
- Determine the empirical formula of the following compounds that underwent combustion analysis.
a. Toluene is composed of C and H and yields 5.86 mg of CO2 and
1.37 mg of H2O after combustion. C7H8
b. 0.1005 g of menthol, which is composed of C, H, and O, yields 0.2829 g
CO2 and 0.1159 g H2O after combustion. C10H20O
- What is the molecular formula of benzoyl peroxide (the empirical formula is
C7H5O2) if the molecular mass is 242 g/mol? C14H10O4
- What are the empirical and molecular formulas of the following compounds?
a. Ibuprofen by mass composition is 75.69% C, 8.80% H and 15.51% O and the
molecular mass is approximately 206 g/mol. C13H18O2
b. Caffeine contains by mass composition 49.5% C, 5.15% H, 28.9% N and 16.5
% O and the molecular mass is about 195 g/mol. C4H5N2O,
C8H10N4O2