Mass & Conversions

Under mass conversions, connections between grams, moles and molecules are established. 

The Mole 

The mole is the chemical unit for the amount of a substance and serves as the bridge that connects grams to molecules, atoms, formula units and ions. 

Mass Conversions

Concept: Avogadro’s Number, Moles, Molecules & Atoms 


The words atoms and ions are used when talking about a single element and the words molecules and formula units are used when talking about more than one element together. 

Example: Determine the mass (in grams) found in 7.28 x 1028 nitrogen atoms.  


Example: Determine the how many molecules of carbon dioxide, CO2, are found in 75.0 g CO2.


Mass Conversion Calculations

Problem: If the density of water is 1.00 g/mL at 25oC calculate the number of water molecules found in 1.50 x 10^3 µL of water.


Problem: Calculate the number of oxygen atoms found in 783.9 g in copper (II) sulfate pentahydrate, CuSO4 x 5 H2O.


Problem: The density of the sun is 1.41 g/cm3 and its volume is 1.41 x 10^27 m3. How many hydrogen molecules are in the sun if we assume all the mass is hydrogen gas?


Problem: 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/cm3. ( V = pi x r^2 x h )