3.2 Determining Empirical and Molecular Formulas
Percent composition by mass, working elemental or combustion data back to an empirical formula, then scaling it up to a molecular formula.
Chemistry 2e, 3.2 Determining Empirical and Molecular Formulas
6 exercises
3.2 Exercise 2
Calculate the following to four significant figures:
(a) the percent composition of ammonia, NH3
(b) the percent composition of photographic fixer solution (“hypo”), Na2S2O3
(c) the percent of calcium ion in Ca3(PO4)2
3.2 Exercise 4
Determine the percent ammonia, NH3, in Co(NH3)6Cl3, to three significant figures.
3.2 Exercise 6
Determine the empirical formulas for compounds with the following percent compositions:
(a) 15.8% carbon and 84.2% sulfur
(b) 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen
3.2 Exercise 8
A compound of carbon and hydrogen contains 92.3% C and has a molar mass of 78.1 g/mol. What is its molecular formula?
3.2 Exercise 10
Determine the empirical and molecular formula for chrysotile asbestos. Chrysotile has the following percent composition: 28.03% Mg, 21.60% Si, 1.16% H, and 49.21% O. The molar mass for chrysotile is 520.8 g/mol.
3.2 Exercise 12
A major textile dye manufacturer developed a new yellow dye. The dye has a percent composition of 75.95% C, 17.72% N, and 6.33% H by mass with a molar mass of about 240 g/mol. Determine the molecular formula of the dye.
Adapted from General Chemistry © 2019 Rice University. Licensed under CC BY 4.0. Sources: Chemistry 2e, Chemistry: Atoms First 2e. Imported at revision 32c7196.