C3

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

  In the top left corner of its nuclear symbol
• What does the mass number represent?

  Number of protons plus neutrons
• What does relative atomic mass (ar) represent?

  Average mass of all isotopes of an element
• What is the relative atomic mass of chlorine?

  35.5
• How do you find the relative formula mass (mr) 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 × number of atoms) / mr × 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%
• What is the formula for 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 relative formula mass 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 are the steps to calculate the percentage mass of an element in a compound?

  1. Identify the relative atomic mass of the element.
  2. Multiply by the number of atoms of that element.
  3. Divide by the relative formula mass of the compound.
  4. Multiply by 100 to convert to percentage.
• What does the term mole refer to in chemistry?

  A unit to measure the amount of substance
• How many particles are in one mole of a substance?

  $6.02 \times 10^{23}$ particles
• What does Avogadro's constant represent?

  The number of particles in one mole
• What is the relative atomic mass of carbon?

  12 grams
• How much does one mole of oxygen weigh if its relative formula mass is 32 grams?

  32 grams
• What is the relative formula mass of carbon dioxide (CO2)?

  44 grams
• What is the formula to calculate the number of moles in a sample?

  Number of moles = mass / relative formula mass
• How many moles are in 42.5 grams of ammonia (NH3)?

  2.5 moles
• What is the mass of 3 moles of carbon dioxide?

  132 grams
• How do you find the mass of carbon in 3 moles of carbon dioxide?

  Multiply 3 moles by 12 grams
• What is the mass of oxygen in 3 moles of carbon dioxide?

  96 grams
• How can chemical equations be interpreted in terms of moles?

  • Chemical equations represent mole ratios.
  • Example: 1 mole of magnesium reacts with 2 moles of hydrochloric acid.
  • Produces 1 mole of magnesium chloride and 1 mole of hydrogen gas.
• If you start with 2 moles of magnesium, how many moles of hydrochloric acid are needed?

  4 moles
• How many moles of magnesium chloride are produced from 2 moles of magnesium?

  2 moles
• How many moles of hydrogen gas are produced from 2 moles of magnesium?

  2 moles