Textbook Question
What is the law of multiple proportions, and how does Dalton's atomic theory account for it?
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Ch.2 - Atoms, Molecules & Ions
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 2, Problem 80
In methane, one part hydrogen combines with three parts carbon by mass. If a sample of a compound containing only carbon and hydrogen contains 32.0 g of carbon and 8.0 g of hydrogen, could the sample be methane? If the sample is not methane, show that the law of multiple proportions is fol-lowed for methane and this other substance.
Verified step by step guidance1
Determine the mass ratio of carbon to hydrogen in methane. Methane (CH₄) has a molar mass of 12.01 g/mol for carbon and 1.01 g/mol for hydrogen. Since there are four hydrogen atoms, the total mass of hydrogen in methane is 4.04 g/mol. Therefore, the mass ratio of carbon to hydrogen in methane is 12.01:4.04.
Calculate the mass ratio of carbon to hydrogen in the given sample. The sample contains 32.0 g of carbon and 8.0 g of hydrogen, so the mass ratio is 32.0:8.0.
Compare the mass ratios. Simplify both ratios to see if they are equivalent. The ratio for methane simplifies to approximately 3:1, while the ratio for the sample simplifies to 4:1.
Since the mass ratios are not the same, the sample is not methane. The sample has a different carbon to hydrogen ratio, indicating it is a different compound.
To show the law of multiple proportions, note that the ratio of the two mass ratios (4:1 for the sample and 3:1 for methane) is a simple whole number ratio, which is consistent with the law of multiple proportions.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Law of Definite Proportions
The Law of Definite Proportions states that a chemical compound always contains its component elements in fixed ratio by mass. For methane (CH4), the ratio of carbon to hydrogen by mass is 12:4 or 3:1. This law helps determine if a given sample could be a specific compound based on its elemental composition.
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Law of Definite Proportions
Law of Multiple Proportions
The Law of Multiple Proportions states that when two elements form more than one compound, the masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers. This principle can be used to compare the ratios of carbon and hydrogen in methane and another compound to demonstrate that they adhere to this law.
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Empirical Formula
The empirical formula of a compound represents the simplest whole-number ratio of the elements present. In the case of the sample with 32.0 g of carbon and 8.0 g of hydrogen, calculating the empirical formula will help determine if it corresponds to methane (CH4) or another compound, thus aiding in the analysis of its composition.
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Related Practice
Textbook Question
A sample of mercury with a mass of 114.0 g was combined with 12.8 g of oxygen gas, and the resulting reaction gave 123.1 g of mercury(II) oxide. How much oxygen was left over after the reaction was complete?
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Textbook Question
A sample of CaCO3 was heated, causing it to form CaO and CO2 gas. Solid CaO remained behind, while the CO2 escaped to the atmosphere. If the CaCO3 weighed 612 g and the CaO weighed 343 g, how many grams of CO2 were formed in the reaction?
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Textbook Question
In borane, one part hydrogen combines with 3.6 parts boron by mass. A compound containing only hydrogen and boron contains 6.0 g of hydrogen and 43.2 g of boron. Could this compound be borane? If it is not borane, show that the law of multiple proportions is followed for borane and this other substance.
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Textbook Question
Benzene, ethane, and ethylene are just three of a large num-ber of hydrocarbons—compounds that contain only carbon and hydrogen. Show how the following data are consistent with the law of multiple proportions.
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Textbook Question
The atomic weight of carbon (12.011) is approximately 12 times that of hydrogen (1.008).(a) Show how you can use this knowledge to calculate pos-sible formulas for benzene, ethane, and ethylene (Prob-lem 2.82).
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