Textbook Question
The diagrams represent a reaction on the molecular level. Atoms of A are represented with red spheres, and atoms of B are represented with blue spheres. Write a balanced chemical equation.
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Ch.3 - Mass Relationships in Chemical Reactions
McMurry8th EditionChemistryISBN: 9781292336145
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Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement170
- Ch.2 - Atoms, Molecules & Ions160
- Ch.3 - Mass Relationships in Chemical Reactions169
- Ch.4 - Reactions in Aqueous Solution199
- Ch.5 - Periodicity & Electronic Structure of Atoms102
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory92
- Ch.7 - Covalent Bonding and Electron-Dot Structures61
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure59
- Ch.9 - Thermochemistry: Chemical Energy122
- Ch.10 - Gases: Their Properties & Behavior155
- Ch.11 - Liquids & Phase Changes54
- Ch.12 - Solids and Solid-State Materials73
- Ch.13 - Solutions & Their Properties120
- Ch.14 - Chemical Kinetics98
- Ch.15 - Chemical Equilibrium125
- Ch.16 - Aqueous Equilibria: Acids & Bases110
- Ch.17 - Applications of Aqueous Equilibria147
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium86
- Ch.19 - Electrochemistry154
- Ch.20 - Nuclear Chemistry96
- Ch.21 - Transition Elements and Coordination Chemistry156
- Ch.22 - The Main Group Elements187
- Ch.23 - Organic and Biological Chemistry51
Chapter 3, Problem 33
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.)
Verified step by step guidance1
Identify the molecular formula of cysteine. Cysteine is composed of carbon (C), hydrogen (H), nitrogen (N), oxygen (O), and sulfur (S). Its molecular formula is typically C3H7NO2S.
Calculate the molar mass of cysteine. Use the atomic masses from the periodic table: C = 12.01 g/mol, H = 1.01 g/mol, N = 14.01 g/mol, O = 16.00 g/mol, S = 32.07 g/mol. Multiply each atomic mass by the number of atoms of that element in the formula and sum them up.
Determine the mass contribution of each element. Multiply the number of atoms of each element by its atomic mass to find the mass contribution of each element in the molecule.
Calculate the percent composition of each element. Divide the mass contribution of each element by the total molar mass of cysteine and multiply by 100 to get the percentage.
Summarize the percent composition. List the percent composition of each element in cysteine: %C, %H, %N, %O, and %S.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molecular Formula
The molecular formula of a compound indicates the types and numbers of atoms present in a molecule. For cysteine, the formula is C3H7N1O2S1, which shows it contains 3 carbon (C), 7 hydrogen (H), 1 nitrogen (N), 2 oxygen (O), and 1 sulfur (S) atom. Understanding the molecular formula is essential for calculating percent composition.
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Determining Molecular Formulas
Percent Composition
Percent composition is a way to express the relative amounts of each element in a compound as a percentage of the total mass. It is calculated by dividing the mass of each element in one mole of the compound by the molar mass of the compound, then multiplying by 100. This concept is crucial for determining the contribution of each element in cysteine.
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Molar Mass Calculation
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To find the molar mass of cysteine, one must sum the molar masses of all its constituent atoms based on the molecular formula. This value is necessary for calculating the percent composition of each element in the amino acid.
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Related Practice
Textbook Question
Fluoxetine, marketed as an antidepressant under the name Prozac, can be represented by the following ball-and-stick molecular model. Write the molecular formula for fluoxetine, and calculate its molecular weight. (Red = O, gray = C, blue = N, yellow green = F, ivory = H.)
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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 difference between a covalent bond and an ionic bond?
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Textbook Question
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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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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