Calculating molar mass from atomic masses

• What is molar mass?

  Mass of one mole of a substance
• What units is molar mass expressed in?

  Grams per mole (g/mol)
• How is molar mass used in chemistry?

  To convert between mass and number of moles
• What is the molar mass of water ($H_{2}O$)?


  Approximately 18 g/mol
• How is the molar mass of water calculated?

  By adding masses of 2 H and 1 O atoms
• What does a chemical formula indicate?

  Elements present and number of atoms
• Why is the chemical formula important for molar mass?

  It helps identify elements and their quantities
• What is the atomic mass of gold ($Au$)?


  Approximately 197 g/mol
• What are the atomic masses of hydrogen and oxygen?

  Hydrogen: 1 g/mol, Oxygen: 16 g/mol
• What are the atomic masses of sodium and chlorine?

  Sodium: 23 g/mol, Chlorine: 35.5 g/mol
• What is the process to calculate molar mass?

  1. Write down the chemical formula.
  2. Identify the subscripts for each element.
  3. Find atomic masses from the periodic table.
  4. Multiply atomic masses by their subscripts.
  5. Sum the results to find total molar mass.
  6. Add units (g/mol) to the final answer.
• How do you find the contribution of sodium in $NaCl$ to its molar mass?


  Multiply 23 g/mol by its subscript 1
• What is the total molar mass of salt ($NaCl$)?


  58.5 g/mol
• Why is it important to include units in molar mass calculations?

  It clarifies the measurement being used
• What is the molar mass of gold ($Au$) after calculation?


  197 g/mol
• What steps are involved in calculating the molar mass of a compound?

  • Identify the chemical formula.
  • Determine atomic masses from the periodic table.
  • Multiply atomic masses by their respective subscripts.
  • Sum the total contributions of each element.
  • Include the units (g/mol) in the final answer.