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Avogadro’s Number is one of the most important constants in chemistry. Corresponding to the number of particles in a single mole, Avogadro’s Number is 6.02214076 × 10 raised to the 23rd power. Read on to learn more about Avogadro’s Number, including who really discovered it and what it’s used for. If it's information you're looking for, we've got your number here!
By analyzing questions, you can see patterns emerge, patterns that will help you answer questions. Qwiz5 is all about those patterns. In each installment of Qwiz5, we take an answer line and look at its five most common clues. Here we explore five clues that will help you answer a tossup on Avogadro’s Number.
LOSCHMIDT
Despite its name, Avogadro’s Number was not discovered by Italian physicist Amadeo Avogadro. The first person to estimate the number of molecules in a given amount of gas was Austrian high school teacher Johann Loschmidt. Loschmidt based his work on an earlier hypothesis of Avogadro’s suggesting that two gases occupying the same volume at the same temperature and pressure contained the same number of particles. Loschmidt’s constant, 2.686 ×10^25 per cubic meter at zero degree centigrade and one atmosphere of pressure is rarely used now but was instrumental in reliably identifying Avogadro’s Number.
12 GRAMS OF CARBON-12
Avogadro’s Number is used to define the unit of measurement known as the mole. A mole is the amount of any single substance containing the same number of elementary entities (atoms, molecules, etc) as there are atoms in 12 grams of Carbon-12. This number of atoms is Avogadro's Number: 6.02214076 × 10^23.
RELATIONSHIP TO THE FARADAY CONSTANT
Avogadro’s Number is used to determine many different values in physical chemistry. One such constant, the Faraday Constant, is defined as the electrical charge of a mole’s worth of elementary charges. An elementary charge is the charge carried by a single proton or electron. The Faraday Constant is calculated by multiplying the elementary charge “e” and Avogadro’s Number.
FORMULATION OF THE IDEAL GAS LAW
Avogadro’s Number is directly involved in the Ideal Gas Law, an equation expressing the relationship between pressure, volume, and temperature of a gas under certain ideal conditions. The equation is expressed as “PV=nRT,” where n is the number of moles of the gas and R is the ideal gas constant. Using these values allows us to see the impact of adding or removing moles of gas on temperature, pressure, or volume provided that two of those three factors are held constant.
X-RAY CRYSTAL DENSITY METHOD
The value of Avogadro’s Number can be determined accurately via a variety of methods. More recently scientists have used a procedure known as the x-ray crystal density method. The constant is determined via x-ray diffraction off a crystal silicon lattice.
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Quizbowl is about learning, not rote memorization, so we encourage you to use this as a springboard for further reading rather than as an endpoint. Here are a few things to check out:
To learn about the many accomplishments of Johann Loschmidt, read this article.
Just how big is a mole? Read this article to learn more.
Michael Faraday had a lot of cool things named after him. Watch this video to learn more.
Want to learn more about x-ray crystallography? Read this article on the practice.
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