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Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 25c

Calculate the percentage by mass of oxygen in the following compounds: (c) acetaminophen, C8H9NO2

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Key Concepts

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

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To calculate the molar mass of a compound, sum the molar masses of all the atoms in its chemical formula. For acetaminophen (C8H9NO2), this involves calculating the contributions from carbon, hydrogen, nitrogen, and oxygen atoms based on their respective atomic weights.
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Percentage by Mass

Percentage by mass is a way to express the concentration of a particular element in a compound. It is calculated by dividing the mass of the element in one mole of the compound by the total molar mass of the compound, then multiplying by 100. This provides a clear understanding of how much of the compound's mass is due to a specific element, such as oxygen in acetaminophen.
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Chemical Composition

Chemical composition refers to the types and quantities of atoms that make up a compound. Understanding the chemical formula of a compound, like C8H9NO2 for acetaminophen, allows one to identify the number of each type of atom present. This is essential for calculating both the molar mass and the percentage by mass of individual elements within the compound.
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