Definitions

• Avogadro's Number is number of molecules in a mole of a single element .
• Molarity is the concentration of a compound, or "solute", in a solution. It is typically expressed in moles/liter.
• Molar Mass is a measure of the mass of one mole of a molecule or element. It is usually expressed in grams/mole.
• Mole Abbreviated mol, a mole is the quantity of a single element such that its mass in grams is equal to its atomic mass. For example, Oxygen has an atomic mass of 15.9994, so a mole of Oxygen has a mass of 15.9994 grams.

Calculating Molar Mass: 

• Calculating a molecule's molar mass requires multiplying the number of each element by its atomic mass.
• Example: Given a water molecule (H20), where the atomic mass of oxygen is 15.9994 and the atomic mass of hydrogen is 1.0079:

  Molar Mass = (1.0079)2 + (15.9994) or 18.0152 grams/mole

Mole Conversions: 

• Converting between the number of moles or mass in grams of a molecule-sample requires first finding molar mass of a single molecule.
• Example: Given a water molecule (H20), where the atomic mass of oxygen is 15.9994 and the atomic mass of hydrogen is 1.0079:

  Molar Mass = (1.0079)2 + (15.9994) or 18.0152 grams/mole

• Once a single molecule's molar mass is found, you can convert between the mass (in grams) and the number of moles.

  Mass of the sample = (molar mass) x (number of moles in the sample)

  Moles in the sample = (Mass of the sample)/(molar mass)

Molarity:

• Molarity is typically expressed as moles/liter.
• Given any two of the molarity, moles of solute, or liters of solution:

  Molarity = (Moles of Solute)/(Liters of Solution)

  Moles of Solute = (Molarity) x (Liters of Solution)

  Liters of Solution = (Moles of Solute)/(Molarity)

Learn more about molarity and stoichiometry with these additional resources:

• Balancing Chemical Equations
  
• Calculating Molar Masses
• Molarity
• Mole Conversions
• Bottomless Worksheet of Molar Masses
• Bottomless Worksheet of Molarity
• Bottomless Worksheet of Mole Conversions
  
• Smartacus Study Sheet