quantitative chemistry

• what is the formula for calculating moles

  $moles\ =$$\ \frac{Mass\ \left(g\right)}{Mr}$
• What does the law of conservation of mass state?

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

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

  Sum of relative atomic masses of atoms
• What must be true in a balanced chemical equation regarding Mr?

  Sum of Mr of reactants equals products
• Why might a reaction appear to involve a change in mass?

  Gas reactant or product not accounted for
• What happens when a metal reacts with oxygen in terms of mass?

  Mass of metal oxide product is greater
• What is always present when a measurement is made?

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

  Make estimations of uncertainty
• What are the key points of the law of conservation of mass?

  • No atoms are lost or created
  • Mass of products equals mass of reactants
  • Chemical equations must be balanced
• What factors can affect the perceived mass change in a chemical reaction?

  • Gas reactants/products not accounted for
  • Measurement errors
  • Changes in state or temperature
• What unit is 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 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 HCl react with one 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
• What are the steps 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
• For calculations, which reactant should be used when a limiting reactant is present?

  The amount of the limiting reactant
• How can concentration of a solution be measured?

  In mass per given volume
• What is the unit for concentration in solutions?

  grams per dm³
• How do you calculate the mass of solute in a solution?

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

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

  It gives a lower concentration
• How do you calculate moles of a reactant?

  Mol = mass / molar mass