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
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Chemistry 2e · 3.2 Determining Empirical and Molecular Formulas
Determining Empirical and Molecular Formulas: practice problems
6 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.
Exercises 35
Determine the percent ammonia, NH₃, in Co(NH₃)₆Cl₃, to three significant figures.
Exercises 37
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
Exercises 39
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?
Exercises 41
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.
Exercises 43
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.
Key terms · 2
- empirical formula mass
- sum of average atomic masses for all atoms represented in an empirical formula
- percent composition
- percentage by mass of the various elements in a compound
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