Related Topics:

Several example molecules are supplied with Avogadro. The screen shot above shows the ethanol.cml file opened up and displayed using the default Ball and Stick display type. Notice that when a new file is opened Avogadro switches from the Draw Tool to the Navigate Tool, which allows you to view the molecule without editing it. Avogadro's number is one of the most important constants used in chemistry. It is the number of particles in a single mole of a material, based on the number of atoms in exactly 12 grams of the isotope carbon-12.

More Lessons for Chemistry
Math Worksheets

• 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.
• Show Step-by-step Solutions
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? 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?
• Show Step-by-step Solutions

The mole and Avogadro's number Atoms, compounds, and ions Chemistry
Avogadro's Number, the Mole and How to Use the Mole