chapter 3

• a mole is defined as an amount of a substance. The number of particles in a mole is 6.02 x 10^23, also known as Avogadro's constant. It can be calculated by doing mass divided by molar mass (mr)
• Molecular formula is the number of atoms of each element in a molecule, whereas empirical formula is the simplest whole number ratio of atoms in elements in a compound. You can calculate empirical formula by writing the mass of elements in a ratio, diving by its ar , then finding the whole number ratio
• Hydrated crystals are formed from an anhydrous salt and water of crystallisation. They are written as salt . x(moles of water). When calculating the moles of these salts, we have to assume all the water has been lost and there is no further decomposition
• 0.001m3=1dm3=1000cm3

  1cm3=1ml
• the concentration is measured as the number of moles of a solute in a measured volume or moles= concentration x volume
• a standard solution is a solution of known concentration
• molar gas volume is the volume per mole of gas molecule at RTP. It is 24dm3

  RTP is 1 atm and 25 degrees Celsius.

  The equation is volume of gas(dm3)= 24dm3 x moles
• Ideal gas equation is pV=nRT

  p= pressure in Pascals

  V= volume in m3

  n= moles

  R= gas constant which is 8.31

  T= temperature in kelvin

  kelvin = degrees in celsius + 273
• stoichiometry is the balancing of the ratio in a reaction
• percentage yield is the : actual yield / theoretical yield x 100

  the actual yield may be smaller due to: the reaction not being completed, other side reactions or loss of product
• the limiting reagent is the reagent that is not in excess and will stop the reactant when completely used up. Calculated by comparing moles.
• the atom economy of a chemical reaction is a measure of how well atoms have been utilised. Calculated by doing:

  mr of desired product/ mr of whole product x 100