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Ch.3 - Molecules and Compounds
All textbooksTro 6th EditionCh.3 - Molecules and CompoundsProblem 79a
Chapter 3, Problem 79a

Calculate the mass percent composition of carbon in each carbon-containing compound. a. CH4 b. C2H6

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Step 1: Identify the molar mass of each element in the compound. The molar mass of carbon (C) is approximately 12.01 g/mol and the molar mass of hydrogen (H) is approximately 1.01 g/mol.
Step 2: Calculate the molar mass of the compound. For CH4, there is one carbon atom and four hydrogen atoms. So, the molar mass of CH4 is (1 * molar mass of C) + (4 * molar mass of H).
Step 3: Calculate the mass percent composition of carbon in the compound. The mass percent composition is calculated by dividing the total mass of carbon in the compound by the molar mass of the compound, then multiplying by 100%.
Step 4: Substitute the values into the formula. The total mass of carbon in CH4 is (1 * molar mass of C). Substitute this value and the molar mass of CH4 into the formula.
Step 5: Simplify the equation to find the mass percent composition of carbon in CH4.

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Key Concepts

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

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all the atoms in a molecule. For example, in methane (CH4), the molar mass is derived from one carbon atom (approximately 12.01 g/mol) and four hydrogen atoms (approximately 1.01 g/mol each), resulting in a total molar mass of about 16.05 g/mol.
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Mass Percent Composition

Mass percent composition is a way to express the concentration of an element in a compound as a percentage of the total mass of the compound. It is calculated using the formula: (mass of the element in the compound / total mass of the compound) x 100%. This concept is essential for understanding the distribution of elements within a compound and is particularly useful in stoichiometry and chemical analysis.
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Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows chemists to predict the amounts of substances consumed and produced in a given reaction. Understanding stoichiometry is crucial for calculating mass percent composition, as it provides the necessary framework for relating the masses of individual elements to the overall mass of the compound.
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