Hey, everyone, we're asked which correctly defines a mole for a, we have the number of entities in a substance. This statement is going to be incorrect because we've learned that a mole of a substance contains Avogadro's number. And this statement doesn't put into account Avogadro's number, which we know is essential to the definition of a mole. For B we have the number of atoms in a substance. This statement is also incorrect for the same reasons why A is incorrect. For C we have the amount of a substance in one g of atoms, molecules formula units particles, et cetera. The statement is also incorrect because again, it is not one g of entities. It has to be Avogadro's number. So for D we have the amount of a substance containing Avogadro's number, which we know to be 6.22 times 10 to the 23rd of atoms, molecules formula units particles, et cetera. So answer choice D correctly defines a mole and is going to be our final answer. Now, I hope this made sense and let us know if you have any questions

Ch.7 Chemical Quantities and Reactions

Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition

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Timberlake 13th Edition

Ch.7 Chemical Quantities and Reactions

Problem 1

Chapter 7, Problem 1

What is a mole?

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A mole is a fundamental concept in chemistry that represents a specific quantity of particles, such as atoms, molecules, or ions. It is used to bridge the microscopic world of atoms and molecules with the macroscopic world we can measure.

The mole is defined as the amount of substance that contains exactly 6.022 × 10^23 particles, known as Avogadro's number. This number is a constant and is used universally in chemistry.

To understand the mole, consider it as a 'chemist's dozen.' Just as a dozen represents 12 items, a mole represents 6.022 × 10^23 particles. This allows chemists to count and measure substances in practical quantities.

The mole is also connected to the concept of molar mass. The molar mass of a substance is the mass of one mole of that substance, expressed in grams per mole (g/mol). It is numerically equal to the atomic or molecular weight of the substance in atomic mass units (amu).

In practice, the mole is used to calculate quantities in chemical reactions, such as determining how many moles of reactants are needed or how many moles of products are formed. This makes it an essential tool for stoichiometry and quantitative chemistry.

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Key Concepts

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

Definition of a Mole

A mole is a fundamental unit in chemistry that quantifies the amount of substance. It is defined as the amount of substance that contains as many entities (atoms, molecules, ions, etc.) as there are in 12 grams of carbon-12. This number is known as Avogadro's number, approximately 6.022 x 10^23.

Avogadro's Number

Avogadro's number is a constant that represents the number of particles in one mole of a substance. It is crucial for converting between the macroscopic scale of grams and the microscopic scale of individual atoms or molecules, allowing chemists to relate mass to the number of particles in a sample.

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 atoms in a molecule, providing a bridge between the mass of a substance and the number of moles, facilitating stoichiometric calculations in chemical reactions.