Relative Formula Mass

• What is meant by relative formula mass?

  It is the sum of the relative atomic masses of the atoms in the numbers shown in the formula.
• How is the relative atomic mass of an element determined?

  By averaging the masses of its isotopes based on their abundance.
• What does the term 'abundance' refer to in the context of isotopes?

  It refers to how common an isotope is.
• What is the atomic number of chlorine?

  17
• Why does chlorine have a relative atomic mass of 35.5?

  Because it averages the masses of its isotopes based on their abundance.
• What is the symbol for relative formula mass?

  Relative formula mass has no specific symbol; it is often represented as M_r.
• Does relative formula mass have units?

  No, relative formula mass has no units.
• What is the relative atomic mass of carbon?

  12
• What is the relative atomic mass of hydrogen?

  1
• How do you calculate the relative formula mass of methane (CH₄)?

  By summing 12 (C) + 4 (H) = 16.
• What is the relative formula mass of methane?

  16
• What happens to the relative formula mass when a coefficient is added in front of a compound's formula?

  It remains the same; coefficients do not affect the relative formula mass calculation.
• How do you calculate the relative formula mass of calcium sulfate (CaSO₄)?

  • 1 atom of calcium (40)
  • 1 atom of sulfur (32)
  • 4 atoms of oxygen (4 x 16 = 64)
  • Total: 40 + 32 + 64 = 136
• How do you calculate the relative formula mass of magnesium hydroxide (Mg(OH)₂)?

  • 1 atom of magnesium (24)
  • 2 atoms of oxygen (2 x 16 = 32)
  • 2 atoms of hydrogen (2 x 1 = 2)
  • Total: 24 + 32 + 2 = 58
• What is the relative formula mass of magnesium hydroxide?

  58
• What should you remember about relative formula mass in exams?

  It has no units and does not involve big numbers in calculations.