Ch.3 - Mass Relationships in Chemical Reactions

McMurry8th EditionChemistryISBN: 9781292336145Not the one you use?Change textbook

McMurry 8th Edition

Ch.3 - Mass Relationships in Chemical Reactions

Problem 34

Chapter 3, Problem 34

Cytosine, a constituent of deoxyribonucleic acid (DNA), can be represented by the following molecular model. If 0.001 mol of cytosine is submitted to combustion analysis, how many moles of CO2 and how many moles of H2O would be formed? (Gray = C, red = O, blue = N, ivory = H.)

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Determine the molecular formula of cytosine by analyzing the molecular model provided.

Identify the number of carbon (C), hydrogen (H), and nitrogen (N) atoms in the cytosine molecule.

Write the balanced chemical equation for the combustion of cytosine, which involves reacting with O2 to form CO2, H2O, and N2.

Use stoichiometry to calculate the moles of CO2 produced from the moles of carbon atoms in 0.001 mol of cytosine.

Use stoichiometry to calculate the moles of H2O produced from the moles of hydrogen atoms in 0.001 mol of cytosine.

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Key Concepts

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

Combustion Analysis

Combustion analysis is a technique used to determine the elemental composition of organic compounds. In this process, a sample is burned in excess oxygen, and the products, typically carbon dioxide (CO2) and water (H2O), are measured. The amounts of these products allow for the calculation of the moles of carbon and hydrogen in the original compound.

Stoichiometry

Stoichiometry is the area of chemistry that deals with the relationships between the quantities of reactants and products in chemical reactions. It is based on the conservation of mass and the balanced chemical equations that represent these reactions. Understanding stoichiometry is essential for calculating the moles of products formed from a given amount of reactants.

Molecular Composition of Cytosine

Cytosine is a nitrogenous base with the molecular formula C4H5N3O. Knowing its molecular composition is crucial for combustion analysis, as it allows for the determination of how many moles of carbon and hydrogen are present in a given amount of cytosine. This information is necessary to calculate the moles of CO2 and H2O produced during combustion.

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What is the difference between a covalent bond and an ionic bond?

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Textbook Question

The following diagram represents the reaction of A₂ (red spheres) with B₂ (blue spheres):

(a) Write a balanced equation for the reaction, and identify the limiting reactant. (b) How many moles of product can be made from 1.0 mol of A₂ and 1.0 mol of B₂?

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Textbook Question

What is the percent composition of cysteine, one of the 20 amino acids commonly found in proteins? (Gray = C, red = O, blue = N, yellow = S, ivory = H.)

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Textbook Question

A hydrocarbon of unknown formula CxHy was submitted to combustion analysis with the following results. What is the empirical formula of the hydrocarbon?

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Textbook Question

Which of the following equations is balanced?