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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 56a
Chapter 3, Problem 56a

(a) The characteristic odor of pineapple is due to ethyl butyrate, a compound containing carbon, hydrogen, and oxygen. Combustion of 2.78 mg of ethyl butyrate produces 6.32 mg of CO2 and 2.58 mg of H2O. What is the empirical formula of the compound?

Verified step by step guidance
1
Determine the mass of carbon in the CO2 produced. Use the molar mass of CO2 (44.01 g/mol) and the fact that each mole of CO2 contains one mole of carbon atoms.
Calculate the mass of hydrogen in the H2O produced. Use the molar mass of H2O (18.02 g/mol) and the fact that each mole of H2O contains two moles of hydrogen atoms.
Subtract the mass of carbon and hydrogen from the total mass of ethyl butyrate combusted to estimate the mass of oxygen in the ethyl butyrate.
Convert the masses of carbon, hydrogen, and oxygen to moles by dividing each by their respective atomic masses (C: 12.01 g/mol, H: 1.008 g/mol, O: 16.00 g/mol).
Divide the moles of each element by the smallest number of moles to find the simplest whole number ratio of atoms of each element, which gives the empirical formula.

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 relative amounts of each element, typically expressed in terms of moles. For example, if a compound contains carbon, hydrogen, and oxygen in a ratio of 1:2:1, its empirical formula would be CH2O.
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Combustion Analysis

Combustion analysis is a method used to determine the composition of organic compounds by burning them in excess oxygen. The products of combustion, typically carbon dioxide (CO2) and water (H2O), are measured to calculate the amounts of carbon and hydrogen in the original compound. This technique is essential for deriving the empirical formula from the mass of the combustion products.
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Stoichiometry

Stoichiometry is the area of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows chemists to calculate the amounts of substances consumed and produced in a reaction based on balanced chemical equations. Understanding stoichiometry is crucial for converting mass measurements into moles and determining the empirical formula from experimental data.
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Related Practice
Textbook Question

Valproic acid, used to treat seizures and bipolar disorder, is composed of C, H, and O. A 0.165-g sample is combusted to produce 0.166 g of water and 0.403 g of carbon dioxide. What is the empirical formula for valproic acid?

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Textbook Question

Washing soda, a compound used to prepare hard water for washing laundry, is a hydrate, which means that a certain number of water molecules are included in the solid structure. Its formula can be written as Na2CO3 # xH2O, where x is the number of moles of H2O per mole of Na2CO3. When a 2.558-g sample of washing soda is heated at 125 C, all the water of hydration is lost, leaving 0.948 g of Na2CO3. What is the value of x?

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Textbook Question

Propenoic acid, C3H4O2, is a reactive organic liquid that is used in the manufacturing of plastics, coatings, and adhesives. An unlabeled container is thought to contain this liquid. A 0.275-g sample of the liquid is combusted to produce 0.102 g of water and 0.374 g carbon dioxide. Is the unknown liquid propenoic acid? Support your reasoning with calculations.

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Textbook Question

(a) Combustion analysis of toluene, a common organic solvent, gives 5.86 mg of CO2 and 1.37 mg of H2O. If the compound contains only carbon and hydrogen, what is its empirical formula?

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Textbook Question

(b) Menthol, the substance we can smell in mentholated cough drops, is composed of C, H, and O. A 0.1005-g sample of menthol is combusted, producing 0.2829 g of CO2 and 0.1159 g of H2O. What is the empirical formula for menthol? If menthol has a molar mass of 156 g/mol, what is its molecular formula?

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Textbook Question

Determine the empirical and molecular formulas of each of the following substances: (b) Cadaverine, a foul-smelling substance produced by the action of bacteria on meat, contains 58.55% C, 13.81% H, and 27.40% N by mass; its molar mass is 102.2 g/mol.

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