7.1: The Mole

What is the mole used for in chemistry?

To count particles such as atoms, molecules, and ions.

What is Avogadro's number?

6.022 × 10²³ items.

How many atoms are in 1 mole of any element?

6.022 × 10²³ atoms.

How many molecules are in 1 mole of a molecular compound?

6.022 × 10²³ molecules.

How many formula units are in 1 mole of an ionic compound like NaCl?

6.022 × 10²³ formula units.

How do you use Avogadro’s number as a conversion factor?

By converting between moles and the number of particles (atoms, molecules, or formula units).

Convert 4.00 mol of iron (Fe) to atoms of iron using Avogadro's number.

4.00 mol Fe * (6.022 × 10²³ atoms Fe / 1 mol Fe) = 2.41 × 10²⁴ atoms Fe.

Convert 3.01 × 10²⁴ molecules of CO₂ to moles of CO₂ using Avogadro's number.

3.01 × 10²⁴ molecules CO₂ * (1 mol CO₂ / 6.022 × 10²³ molecules CO₂) = 5.00 mol CO₂.

How many molecules are present in 1.75 mol of CO₂?

1.75 mol CO₂ * (6.022 × 10²³ molecules CO₂ / 1 mol CO₂) = 1.05 × 10²⁴ molecules CO₂.

What do the subscripts in a chemical formula indicate?

The number of atoms of each type of element in a compound.

How many carbon, hydrogen, and oxygen atoms are in a molecule of aspirin (C₉H₈O₄)?

9 carbon atoms, 8 hydrogen atoms, and 4 oxygen atoms.

How many moles of each element are in 1 mol of aspirin (C₉H₈O₄)?

9 mol of C atoms, 8 mol of H atoms, and 4 mol of O atoms.

Write the conversion factors for the elements in 1 mol of aspirin (C₉H₈O₄).

• 9 mol C / 1 mol C₉H₈O₄

• 8 mol H / 1 mol C₉H₈O₄

• 4 mol O / 1 mol C₉H₈O₄

How do you use subscripts from a formula to write conversion factors?

Use the subscript values as the number of moles of each element per mole of the compound.