Moles & Mass

• How many particles are in one mole of a substance?

  $6.02 \times 10^{23}$ particles
• What does the term mole refer to in chemistry?

  A unit to measure the amount of substance
• What does Avogadro's constant represent?

  The number of particles in one mole
• If you have one mole of carbon, how many atoms are present?

  $6.02 \times 10^{23}$ atoms of carbon
• Why does one mole of a substance weigh the same as its relative atomic or formula mass in grams?

  Because of the definition of the mole
• What is the relative atomic mass of carbon?

  12
• What is the relative formula mass of oxygen in O₂?

  32
• How do you calculate the number of moles in a sample?

  Mass divided by relative formula mass
• How many moles are in 42.5 grams of ammonia?

  1. 5 moles
• What is the molar mass of ammonia (NH₃)?

  17
• 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 moles by carbon's molar mass
• What is the mass of carbon in 3 moles of carbon dioxide?

  36 grams
• How do you find the mass of oxygen in carbon dioxide?

  Subtract carbon mass from total mass
• How can chemical equations be interpreted in terms of moles?

  As ratios of reactants and products
• If you start with 2 moles of magnesium, how many moles of hydrochloric acid are needed?

  4 moles
• What is produced when magnesium reacts with hydrochloric acid?

  Magnesium chloride and hydrogen gas
• What is the relationship between moles, mass, and relative formula mass?

  • Number of moles = mass / relative formula mass
  • Mass = number of moles × relative formula mass
• What are the steps to calculate the mass of an element in a compound?

  1. Determine the number of moles of the compound.
  2. Multiply by the molar mass of the element.
  3. Subtract from the total mass to find the mass of other elements.
• What is the significance of chemical equations in terms of moles?

  • They represent the ratios of reactants and products.
  • They help in stoichiometric calculations.