Mole, Avogadro Constant & Molar Mass

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Mole, Mass & Avogadro Constant

• An amount of substance containing 6.02 × 10²³ particles is called a mole (often abbreviated to mol).
• 6.02 × 10²³ is called the Avogadro Constant or Avogadro's Number.

The following diagram shows how to convert between Mass, Mole and Number of particles. Scroll down the page for more examples and solutions.

Example:

One mole of carbon contains 6.02 × 10²³ of carbon atoms.
One mole of oxygen contains 6.02 × 10²³ of oxygen molecules

Molar mass

• The mass of one mole of a substance is called the molar mass.
• The molar mass of a substance is equal to its relative formula mass in grams.

Example:
What is the mass of 1 mole of carbon?

Solution:
The mass of 1 mole of carbon = relative formula mass of carbon = 12 grams

Example:
What is the molar mass of calcium carbonate (CaCO₃)?

Solution:

Step 1: Look up the relative atomic masses of the atoms from the periodic table.
Relative atomic mass (rounded to the nearest whole number):
Ca = 40, C = 12, O = 16

Step 2: Calculate the relative formula mass.
Calcium carbonate (CaCO₃) contains one calcium atom, one carbon atom and three oxygen atoms.
Relative formula mass = 40 + 12 + (3 × 16) = 100

Step 3: Express the relative formula mass in grams per mole.
The molar mass of ethanol is 100 g/mol

Example:
What is the molar mass of ethanol (C₂H₅OH)?

Solution:
Step 1: Look up the relative atomic masses of the atoms from the periodic table.
Relative atomic mass (rounded to the nearest whole number):
H = 1, C = 12, O = 16

Step 2: Calculate the relative formula mass.
Ethanol (C₂H₅OH) contains two carbon atoms, six hydrogen atoms and one oxygen atom.
Relative formula mass = (2 × 12) + (6 × 1) + 16 = 46

Step 3: Express the relative formula mass in grams per mole.
The molar mass of ethanol is 46 g/mol

Introduction to Moles A mole is like a dozen. It is a name for a specific number of things. There are 12 things in a dozen, and 602 hexillion things in a mole.
What are moles and why they are important?
How to abbreviate the mole number (Avogadro's number) using scientific notation, and compare to see how giant this number is.

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Converting Between Moles, Atoms, and Molecules
How to convert between moles and the number of atoms or molecules using both a common sense approach, and a standard conversion factor method?
How to round our answers with scientific notation and significant figures?
Example:
How many atoms in 5.5 moles?
How many moles is 4.6 × 10²⁴ sulfur atoms?

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Converting between Moles, Atoms, and Molecules (Part 2)
More practice problems, converting between moles, atoms, and molecules.
Example:
How many molecules is 0.63 moles of molecules?
How many moles is 3.9 × 10²⁰ Magnesium atoms?

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The mole and Avogadro's number | Atoms, compounds, and ions | Chemistry

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Avogadro's Number, the Mole and How to Use the Mole
Avogadro's gas law, Avogadro's number, the MOLE and molar mass.

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