Masses and Moles

• What is the unit used to measure chemical amounts?

  Moles
• What is the symbol for the unit mole?

  mol
• How is the mass of one mole of a substance related to its relative formula mass?

  The mass in grams is numerically equal to its relative formula mass.
• If the Mr of iron is 56, what is the mass of one mole of iron?

  56g
• What is the mass of one mole of nitrogen gas, N2, if its Mr is 28?

  28g
• What does one mole of a substance contain in terms of particles?

  It contains the same number of particles as one mole of any other substance.
• What is the Avogadro constant?

  1. 02 x 10²³ per mole
• How can masses of reactants and products be calculated?

  From balanced symbol equations.
• How can chemical equations be interpreted in terms of moles?

  They show the ratio of moles of reactants and products.
• In the equation Mg + 2HCl -> MgCl₂ + H₂, how many moles of HCl react with 1 mole of Mg?

  2 moles
• What must be true about the total moles of one element in a balanced equation?

  They must be the same on both sides of the equation.
• What are the steps to balance a chemical equation using moles?

  1. Convert the masses in grams to amounts in moles.
  2. Convert the numbers of moles to simple whole number ratios.
  3. Determine how many moles you have of one element/compound compared to another.
• What is a limiting reactant in a chemical reaction?

  The reactant that is used up and limits the amount of products formed.
• What happens if a limiting reactant is used in a reaction?

  The amount of product produced is restricted to the amount of the limiting reactant that reacts.
• How can concentration of a solution be measured?

  In mass per given volume, e.g., grams per dm³ (g/dm³).
• What is the formula to calculate the mass of solute in a solution?

  mass = concentration x volume
• What effect does a smaller volume or larger mass of solute have on concentration?

  It gives a higher concentration.
• What effect does a larger volume or smaller mass of solute have on concentration?

  It gives a lower concentration.