Ch.3 - Chemical Reactions and Reaction Stoichiometry

Brown - Chemistry: The Central Science 14th Edition

Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook

Brown 14th Edition

Ch.3 - Chemical Reactions and Reaction Stoichiometry

Problem 26b

Chapter 3, Problem 26b

Calculate the percentage by mass of the indicated element in the following compounds: (b) oxygen in vitamin E, C29H50O2

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Identify the molar mass of each element in the compound: Carbon (C), Hydrogen (H), and Oxygen (O).

Calculate the total molar mass of the compound C29H50O2 by summing the molar masses of all atoms present.

Determine the total mass of oxygen in the compound by multiplying the number of oxygen atoms by the molar mass of oxygen.

Calculate the percentage by mass of oxygen by dividing the total mass of oxygen by the total molar mass of the compound and then multiplying by 100.

Express the result as a percentage to find the percentage by mass of oxygen in vitamin E.

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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 vitamin E (C29H50O2), this involves calculating the contributions from carbon, hydrogen, and oxygen atoms based on their respective atomic weights.

Percentage by Mass

Percentage by mass is a way to express the concentration of an element within a compound. It is calculated by dividing the mass of the element of interest by the total mass of the compound, then multiplying by 100. This calculation helps in understanding the composition of compounds and is essential for stoichiometric calculations in chemistry.

Chemical Formula Interpretation

A chemical formula provides information about the types and numbers of atoms in a molecule. In the case of vitamin E, C29H50O2, the formula indicates that the molecule contains 29 carbon atoms, 50 hydrogen atoms, and 2 oxygen atoms. Understanding how to interpret chemical formulas is crucial for performing calculations related to the composition and properties of compounds.

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