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Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 4

The following diagram represents the collection of CO2 and H2O molecules formed by complete combustion of a hydrocarbon. What is the empirical formula of the hydrocarbon?

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Identify the number of CO2 and H2O molecules in the diagram.
Determine the number of carbon atoms from the CO2 molecules, since each CO2 molecule contains one carbon atom.
Determine the number of hydrogen atoms from the H2O molecules, since each H2O molecule contains two hydrogen atoms.
Assume the hydrocarbon is CxHy, where x is the number of carbon atoms and y is the number of hydrogen atoms.
Divide the number of carbon and hydrogen atoms by their greatest common divisor to find the simplest whole number ratio, which gives the empirical formula.

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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 molecular formula by dividing the subscripts of each element by their greatest common divisor. For hydrocarbons, which consist of carbon (C) and hydrogen (H), the empirical formula provides insight into the basic composition of the molecule.
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Combustion Reaction

A combustion reaction is a chemical process in which a hydrocarbon reacts with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O). This reaction is exothermic, releasing energy in the form of heat and light. Understanding the products of combustion is essential for determining the composition of the original hydrocarbon and subsequently its empirical formula.
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Hydrocarbon Structure

Hydrocarbons are organic compounds composed solely of carbon and hydrogen atoms. They can be classified into aliphatic (alkanes, alkenes, alkynes) and aromatic hydrocarbons. The structure of a hydrocarbon influences its combustion products and the ratio of carbon to hydrogen, which is crucial for calculating the empirical formula based on the amounts of CO2 and H2O produced during combustion.
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