1.1.4

Avogadro's Constant

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Moles

The amount of a substance is measured using a unit called a mole (mol).

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What is a mole?

  • A mole is simply a massive number of particles.
  • You can have a mole of anything: laptops, sunglasses and, of course, atoms (this is what we care about!).
  • A mole of things contains 6.02 ×1023 things.
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Carbon-12

  • The value of the mole is set so that a mole of carbon-12 atoms weighs 12 grams.
  • This is important because the mass of one carbon-12 atom is 12 amu.
  • So the mole converts between amu and grams:
    • 1 g = 1 mol × 1 amu
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Convenience

  • Atoms are really tiny and so it's very difficult to measure a single atom.
  • By using the mole, we can do calculations about the amount of stuff we have in any reaction.
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Avogadro's constant

  • The value of Avogadro's constant is 6.02 ×1023.
  • So one mole contains Avogadro's constant of things.
    • Number of particles = number of moles × Avogadro's constant

Jump to other topics

1Physical Quantities & Units

2Measurement Techniques

3Kinematics

4Dynamics

5Gravitational Fields

6Deformation of Solids

7Thermal Physics

8Oscillations

9Communication

10Electric Fields

11Current Electricity

12Magnetic Fields

13Modern Physics

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