Relative Formula Mass

• What is the topic of today's video?

  Relative formula mass calculations
• How can we find the mass number of an element?

  By looking in the top left corner of its nuclear symbol
• What does the mass number represent?

  Number of protons plus neutrons
• What is relative atomic mass denoted by?

  ar
• What is the relative atomic mass of chlorine as an element?

  35.5
• How do you find the relative formula mass of a compound?

  Add relative atomic masses of all atoms
• What is the molecular formula of magnesium chloride?

  MgCl₂
• What is the relative atomic mass of magnesium?

  24
• What is the calculation for the relative formula mass of magnesium chloride?

  24 + 35.5 × 2
• What is the relative formula mass of magnesium chloride?

  95
• What is the molecular formula of sulfuric acid?

  H₂SO₄
• How do you calculate the relative formula mass of sulfuric acid?

  2 × 1 + 32 + 4 × 16
• What is the relative formula mass of sulfuric acid?

  98
• How do you calculate the percentage mass of an element in a compound?

  AR of element × number of atoms / MR of compound × 100
• What is the AR of sulfur?

  32
• How many atoms of sulfur are in sulfuric acid?

  1
• What is the calculation for the percentage mass of sulfur in sulfuric acid?

  32 × 1 / 98 × 100
• What is the percentage mass of sulfur in sulfuric acid?

  32.7%
• What is the formula of calcium hydroxide?

  Ca(OH)₂
• What is the relative atomic mass of calcium?

  40
• What is the relative atomic mass of oxygen?

  16
• What is the relative atomic mass of hydrogen?

  1
• How do you calculate the percentage mass of oxygen in calcium hydroxide?

  16 × 2 / MR × 100
• What is the MR of calcium hydroxide?

  74
• What is the percentage mass of oxygen in calcium hydroxide?

  43.2%
• What are the steps to calculate the relative formula mass of a compound?

  1. Identify the molecular formula.
  2. Find the relative atomic masses of each element.
  3. Multiply the relative atomic mass by the number of atoms.
  4. Sum all the values to get the relative formula mass.
• What is the process to calculate the percentage mass of an element in a compound?

  1. Find the relative atomic mass (AR) of the element.
  2. Multiply AR by the number of atoms of that element.
  3. Divide by the relative formula mass (MR) of the compound.
  4. Multiply by 100 to convert to percentage.