Amount of Substance

• Define amount of substance.

  The number of particles in a substance.
• Define moles.

  1 mole is the amount of substance which contains as many particles as there are atoms in exactly 12g of carbon-12.
• What is the number for Avogadro’s Constant ?

  6.022 x 10*23
• Units for molar mass.


  g mol-1
• Units for molar gas volume.

  dm3 mol-1
• Define empirical formula.

  The simplest whole number ratio of atoms of each element present in a compound.
• Define molecular formula.

  The actual number of atoms of each element in a molecule.
• What is Stoichiometry ?

  The relationship between the amounts of reactants and products.
• How are hydrated salts converted into anhydrous salts ? What is this process called ?

  heating to drive off H2O - waters of crystallisation
• How can you be certain that all the water of crystallisation had been removed ?

  Heat until constant mass
• 1 tonne = ? g

  1 x 10*6
• What is a solution ?

  A solute dissolved in a solvent.
• What is a standard solution ?

  A solution of known concentration.
• What are the units for concentration ?

  moldm-3
• What does a concentrated solution mean ?

  A solution containing a higher number of moles of solute in a given volume of solution.
• What does a dilute solution mean ?

  A solution containing a fewer number of moles of solute in a given volume of solution.
• The ideal gas equation :

  PV = nRT
• Convert kPa to Pa

  x1000
• Convert dm3 to m3

  /1000
• Convert cm3 to m3

  /1,000,000
• Convert *C into K

  +273
• Why do reactions give yields of less than 100% ?

  • Reaction may be incomplete
  • There may be side reaction producing side products
  • Recovery of all products from a reaction is impossible
  • Some products are lost during transfer of chemicals, and as the product is separated and purified
• Equation for % yield :

  %yield = (Actual mol / Theoretical mol) x100
• What is atom economy ?

  Compares how many of the reactant atoms end up in the desired products, as compared to waste products and other by-products.
• What are the benefits of high atom economy ?

  • minimal waste
  • less waste in landfills
  • reduces costs on waste treatment
• Equation for Atom Economy :

  Atom Economy = (mr of desired products / sum of mr of all poducts ) x100