Practice: If a sample of sodium chloride, NaCl, contains 73.1 kg, what is its number of formula units?

The **Mole Concept** involves the interconversions between different unit amounts of a substance.

Concept #1: Mole Concept

**Mole **connects together atoms, ions, molecules and formula units.

Example #1: Which of the following compounds would not be associated with the term “formula unit”?

Concept #2: Converting between Moles and Particles

Converting between moles and particles requires Avogadro's Number: **1 mole = 6.022x10 ^{23 }particles.**

Example #2: How many moles of chlorine gas are there in 8.33 x 10^{37} molecules?

Concept #3: Converting between Mass and Moles

Example #3: How many grams of chlorine gas are there in 2.34 moles?

Example #4: How many grams of Cl_{2 }contain 9.25 x 10^{24} molecules of Cl_{2}?

Mole also serves to connect mass units to particles.

Practice: If a sample of sodium chloride, NaCl, contains 73.1 kg, what is its number of formula units?

Practice: Calculate the number of oxygen atoms found in 783.9 g NiCl_{2} • 6 H_{2}O.

Practice: If the density of water is 1.00 g/mL at 25°C, calculate the number of water molecules found in 1.50 x 10^{3} µL of water.

Practice: A cylindrical copper wire is used for the fences around a house. The copper wire has a diameter of 0.0750 in. How many copper atoms are found in 5.160 cm piece? The density of copper is 8.96 g/cm^{3}. (V = π • r^{2} • h)

Practice: The density of the sun is 1.41 g/cm^{3} and its volume is 1.41 x 10^{27} m^{3}. How many hydrogen molecules are in the sun if we assume all the mass is hydrogen gas?