Moles and calculations

• What does the term "mole" refer to in chemistry?


  A unit used to measure the amount of chemical substance
• How is the mole similar to other units of measurement like meters and seconds?

  It measures the amount of substance, just as meters measure distance and seconds measure time
• How many particles are contained in one mole of any substance?

  1. 02 times 10 to the 23 particles
• What does "particles" refer to in the context of moles?

  Atoms, molecules, ions, or electrons depending on the substance
• If you have one mole of carbon, how many atoms of carbon do you have?

  1. 02 times 10 to the 23 atoms of carbon
• What is Avogadro's constant?

  1. 02 times 10 to the 23 particles per mole
• Why is Avogadro's constant significant in chemistry?

  It allows us to relate the mass of a substance to its relative atomic or formula mass in grams
• What is the relative atomic mass of carbon?

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

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

  44
• How do you calculate the number of moles in a sample?

  Number of moles = mass of the element or compound / relative formula mass
• How many moles are in 42.5 grams of ammonia (NH3) with a relative formula mass of 17?

  1. 5 moles
• What is the mass of 3 moles of carbon dioxide (CO2)?

  132 grams
• How do you find the mass of a particular element within a larger compound?

  Multiply the number of moles by the relative atomic mass of that element
• What is the mass of carbon in 3 moles of carbon dioxide (CO2)?

  36 grams
• If you subtract the mass of carbon from the total mass of carbon dioxide, what mass of oxygen do you find?

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

  • Chemical equations represent the ratios of moles of reactants and products.
  • Example: 1 mole of magnesium reacts with 2 moles of hydrochloric acid to produce 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 do you need to react with it?

  4 moles of hydrochloric acid
• How many moles of magnesium chloride and hydrogen gas are produced from 2 moles of magnesium reacting with hydrochloric acid?

  2 moles of magnesium chloride and 2 moles of hydrogen gas