Relative Formula Mass

• What is the topic of today's video?

  Relative formula mass calculations
• Where can you find the mass number of an element?

  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?

  mg cl2
• What is the relative atomic mass of magnesium?

  24
• How do you calculate the relative formula mass of magnesium chloride?

  24 + 35.5 times 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 times 1 + 32 + 4 times 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 times number of atoms divided by mr times 100
• What is the relative atomic mass of sulfur?

  32
• What is the relative formula mass of sulfuric acid used in the percentage calculation?

  98
• What is the percentage mass of sulfur in sulfuric acid?

  32.7 percent
• What is the formula for calcium hydroxide?

  ca oh2
• What is the relative atomic mass of calcium?

  40
• What is the relative atomic mass of oxygen?

  16
• How do you calculate the percentage mass of oxygen in calcium hydroxide?

  16 times 2 divided by mr times 100
• What is the relative formula mass of calcium hydroxide?

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

  43.2 percent
• 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. Add the relative atomic masses of all atoms in the formula.
• What is the process to find the percentage mass of an element in a compound?

  1. Use the formula:

  • (ar of element × number of atoms) / mr of compound × 100

  1. Calculate to get the percentage.