Topic 3: Quantitative Chemistry

• What is the actual yield in a chemical reaction?

  The amount of product actually produced
• What does atom economy measure?

  Useful products from starting materials
• What is the Avogadro constant?

  Number of atoms in a mole
• What does Avogadro's law state about gases?

  Equal moles occupy the same volume
• How is concentration defined in chemistry?

  Amount of substance in a volume of solution
• What does the law of conservation of mass state?

  No atoms are lost or made in reactions
• What is a limiting reactant?

  The reactant completely used up
• What is the unit for measuring chemical amounts?

  Mole
• How is percentage by mass calculated?

  Mass of component divided by total mass
• What does percentage yield compare?

  Actual yield to theoretical yield
• What is relative formula mass?

  Sum of relative atomic masses in a formula
• What is the theoretical yield?

  Maximum product from given reactants
• What is thermal decomposition?

  Breakdown of a compound when heated
• What does uncertainty in measurements refer to?

  Degree of doubt in measurement accuracy
• How can uncertainty arise in measurements?

  From equipment limitations or experimenter skill
• What does the law of conservation of mass state?

  No atoms are lost or made in reactions
• What does it mean for a chemical equation to be balanced?

  Same number of atoms on both sides
• How is relative formula mass (Mr) calculated?

  Sum of relative atomic masses in formula
• What is the relative formula mass of HCl?

  $36.5$
• What must be true in a balanced chemical equation regarding Mr?

  Sum of Mr of reactants equals products
• What happens to mass when a gas is involved in a reaction?

  Mass may appear to change if gas is lost
• What should you check if a reaction shows a mass change?

  Whether a gas was released or not
• What is an example of a mass change in a reaction?

  Metal oxide product mass greater than metal
• What is always present in measurements made in chemistry?

  Some uncertainty about the result
• What should you be prepared to do regarding measurement uncertainty?

  Make estimations of uncertainty
• What is the unit for measuring chemical amounts?

  Mole
• What is the symbol for the unit mole?

  mol
• How is the mass of one mole of a substance expressed in grams?

  It equals its relative formula mass
• What is the mass of one mole of iron?

  56g
• How much does one mole of nitrogen gas weigh?

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

  The same number of particles as any mole
• What is the Avogadro constant?

  6.02 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
• In the equation Mg + 2HCl -> MgCl₂ + H₂, how many moles of Mg react?

  1 mole
• In the equation Mg + 2HCl -> MgCl₂ + H₂, how many moles of HCl react?

  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
• What is the process to balance a chemical equation using moles?

  1. Convert masses in grams to moles
  2. Convert moles to simple whole number ratios
  3. Determine the number of moles of each element/compound
• What is a limiting reactant?

  The reactant that is used up first
• What happens if a limiting reactant is used in a reaction?

  It restricts the amount of product produced