1.2 - Amount of Substance

• What is the key concept for chemical calculations?

  The mole
• How is the mole defined in terms of carbon-12?

  Amount of substance in grams equal to 12g of carbon-12
• What is Avogadro's Number?

  6.022 x 10²³
• What does one mole of any specified entity contain?

  6.022 x 10²³ of that entity
• What are the three equations used to calculate moles at A-level?

  1. For pure solids, liquids, and gases
  2. For gases: PV = nRT
  3. For solutions
• What is the unit of mass in chemical calculations?

  Grams
• What is the unit of moles?

  mol
• What is the unit of pressure (P)?

  Pa
• What is the unit of volume (V)?

  m³
• What is the unit of temperature (T)?

  K
• What is the value of R in the gas equation?

  8.31
• What is the unit of concentration?

  mol dm^-3 or M
• How do you convert cm³ to dm³?

  Divide by 1000
• How do you convert cm³ to m³?

  Divide by 1,000,000
• How do you convert dm³ to m³?

  Divide by 1000
• How do you convert °C to K?

  Add 273
• What is relative atomic mass?

  Average mass of one atom compared to carbon-12
• What is relative molecular mass?

  Average mass of a molecule compared to carbon-12
• To how many decimal places must Mr be quoted?

  1 decimal place
• How do you calculate the number of moles of CuSO₄ in 35.0g?

  moles = mass / Mr
• What is the molar mass (Mr) of CaCO₃?

  100.1
• How should answers be given in terms of significant figures?

  Same as the smallest significant figures given
• How many mg are in 1g?

  1000 mg
• How many g are in 1 kg?

  1000 g
• How many kg are in 1 tonne?

  1000 kg
• How do you calculate the number of moles in 75.0 mg of CaSO₄.2H₂O?

  moles = mass / Mr
• What is the number of chloride ions in 25.0 cm³ of magnesium chloride solution?

  1.20 x 10²² ions
• What is the density unit typically used?

  g cm^-3
• How do you calculate the number of molecules of ethanol in 0.500 dm³ of ethanol?

  moles = mass / Mr
• How do you calculate the density of gold in kg dm^-3?

  density = mass / volume
• What is the definition of a molecular formula?

  Actual number of atoms of each element
• How do you determine the molecular formula from the empirical formula?

  Divide Mr by mass of empirical formula
• What is the empirical formula for a compound with 1.82g of K, 5.93g of I, and 2.24g of O?

  KIO₃
• What is the first step to calculate the empirical formula?

  Divide each mass by atomic mass
• What is the second step to calculate the empirical formula?

  Divide by the smallest number of moles
• What is the third step to calculate the empirical formula?

  Multiply to give whole numbers if needed
• How do you calculate the mass of water lost in a reaction?

  Initial mass - final mass
• How do you calculate the value of x in ZnSO₄.xH₂O?

  Calculate moles of ZnSO₄ and H₂O
• What is a hydrated salt?

  A salt containing water of crystallisation
• What is the unit of concentration in solutions?

  mol dm^-3 or M