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Ch.3 - Chemical Reactions and Reaction Stoichiometry
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.3 - Chemical Reactions and Reaction StoichiometryProblem 46a
Chapter 3, Problem 46a

Determine the empirical formula of each of the following compounds if a sample contains (a) 3.92 mol C, 5.99 mol H, and 2.94 mol O

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1
Determine the smallest number of moles among the given elements. In this case, it is 2.94 mol of O.
Divide the number of moles of each element by the smallest number of moles to simplify the mole ratio. For C: 3.92 mol / 2.94 mol, for H: 5.99 mol / 2.94 mol, for O: 2.94 mol / 2.94 mol.
Round each result to the nearest whole number to find the simplest whole number ratio of atoms. This will give you the subscripts for each element in the empirical formula.
Construct the empirical formula by writing the symbols of each element followed by their respective subscript obtained in the previous step (if the subscript is 1, it is typically omitted).
Verify the empirical formula by ensuring that the total number of atoms in the formula corresponds to the ratios calculated from the original mole amounts.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Empirical Formula

The empirical formula of a compound represents the simplest whole-number ratio of the elements present in that compound. It is derived from the number of moles of each element, providing a basic understanding of the composition without indicating the actual number of atoms in a molecule.
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Mole Concept

The mole is a fundamental unit in chemistry that quantifies the amount of substance. One mole corresponds to Avogadro's number, approximately 6.022 x 10²³ entities (atoms, molecules, etc.). Understanding the mole concept is essential for converting between mass, number of particles, and volume in chemical calculations.
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Mole Ratio

Mole ratio refers to the relative number of moles of each element in a compound. It is crucial for determining the empirical formula, as it allows chemists to simplify the ratios of the elements to their smallest whole numbers, which is necessary for accurately representing the composition of the compound.
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Related Practice
Textbook Question

Determine the empirical formulas of the compounds with the following compositions by mass: (b) 57.5% Na, 40.0% O, and 2.5% H (c) 41.1% N, 11.8% H, and the remainder S

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Textbook Question

Give the empirical formula of each of the following compounds if a sample contains (b) 2.10 g nickel and 0.58 g oxygen

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Textbook Question

Determine the empirical formulas of the compounds with the following compositions by mass: (c) 60.0% C, 4.4% H, and the remainder O

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At least 25 mg of tetrahydrocannabinol (THC), the active ingredient in marijuana, is required to produce intoxication. The molecular formula of THC is C21H30O2. How many molecules?

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Textbook Question

Determine the empirical formulas of the compounds with the following compositions by mass: (a) 74.0% C, 8.7% H, and 17.3% N

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Textbook Question

Give the empirical formula of each of the following compounds if a sample contains (c) 26.56% K, 35.41% Cr, and 38.03% O by mass.

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