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Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 88a

If 2.0 mol CH3CH2CH2COOH, 2.0 mol C4H10, and 2.0 mol C6H6 are completely combusted in oxygen, which one produces the largest number of moles of H2O?

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1
Identify the chemical formulas for each compound: CH3CH2CH2COOH (butanoic acid), C4H10 (butane), and C6H6 (benzene).
Write the balanced chemical equation for the complete combustion of each compound. For example, the combustion of butanoic acid is: \[ \text{CH}_3\text{CH}_2\text{CH}_2\text{COOH} + \frac{9}{2} \text{O}_2 \rightarrow 4 \text{CO}_2 + 4 \text{H}_2\text{O} \]
Determine the number of moles of water produced per mole of each compound combusted. For butanoic acid, 4 moles of water are produced per mole of acid.
Calculate the total moles of water produced by multiplying the moles of each compound by the moles of water produced per mole of compound. For example, for butanoic acid: \(2.0 \text{ mol} \times 4 \text{ mol H}_2\text{O/mol} = 8 \text{ mol H}_2\text{O}\).
Compare the total moles of water produced by each compound to determine which one produces the largest number of moles of water.

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Key Concepts

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

Combustion Reaction

A combustion reaction is a chemical process in which a substance reacts with oxygen to produce heat and light. In organic compounds, this typically results in the formation of carbon dioxide and water. Understanding the stoichiometry of combustion reactions is essential for determining the products and their quantities, particularly when comparing different substances.
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Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It allows us to determine the mole ratios of substances involved in the reaction, which is crucial for predicting how many moles of water will be produced from the combustion of each hydrocarbon in the question.
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Molar Mass and Molecular Formula

The molar mass and molecular formula of a compound provide information about the number of atoms of each element in a molecule. For hydrocarbons like CH3CH2CH2COOH, C4H10, and C6H6, knowing their molecular formulas helps in calculating the total number of moles of water produced during combustion, as the number of hydrogen atoms directly influences the amount of water formed.
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