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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 19c
Chapter 3, Problem 19c

Write a balanced chemical equation for the reaction that occurs when (c) the hydrocarbon styrene, C8H81l2, is combusted in air

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Identify the reactants and products in the combustion reaction. The reactants are styrene \( \text{C}_8\text{H}_8 \) and oxygen \( \text{O}_2 \), and the products are carbon dioxide \( \text{CO}_2 \) and water \( \text{H}_2\text{O} \).
Write the unbalanced chemical equation: \( \text{C}_8\text{H}_8 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O} \).
Balance the carbon atoms first. There are 8 carbon atoms in styrene, so you need 8 \( \text{CO}_2 \) molecules: \( \text{C}_8\text{H}_8 + \text{O}_2 \rightarrow 8\text{CO}_2 + \text{H}_2\text{O} \).
Balance the hydrogen atoms next. There are 8 hydrogen atoms in styrene, so you need 4 \( \text{H}_2\text{O} \) molecules: \( \text{C}_8\text{H}_8 + \text{O}_2 \rightarrow 8\text{CO}_2 + 4\text{H}_2\text{O} \).
Finally, balance the oxygen atoms. Count the total oxygen atoms needed on the right side (8 \( \text{CO}_2 \) gives 16 O, and 4 \( \text{H}_2\text{O} \) gives 4 O, totaling 20 O). Therefore, you need 10 \( \text{O}_2 \) molecules on the left: \( \text{C}_8\text{H}_8 + 10\text{O}_2 \rightarrow 8\text{CO}_2 + 4\text{H}_2\text{O} \).

Key Concepts

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

Combustion Reactions

Combustion reactions involve the reaction of a substance with oxygen, typically producing heat and light. In organic chemistry, hydrocarbons combust to form carbon dioxide and water. Understanding the general form of combustion reactions is essential for writing balanced equations.
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Balancing Chemical Equations

Balancing chemical equations ensures that the number of atoms for each element is the same on both sides of the equation, adhering to the law of conservation of mass. This process involves adjusting coefficients in front of compounds to achieve balance, which is crucial for accurately representing chemical reactions.
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Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It allows chemists to calculate the amounts of substances consumed and produced, which is vital when balancing equations and predicting the outcomes of reactions, such as combustion.
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