1.2 Amount of Substance

• how do you calculate moles from mass and Mr?

  Number of moles = mass (g) / Mr
• how do you work out the mass of a single atom?

  Atomic mass / avogadro's number (6.022 x 1023)
• how do you calculate the moles of a substance in a solution?

  number of moles = concentration (mol dm-3) x volume (dm-3)
• what is the ideal gas equation?

  the number of moles in a specific volume of a gas

  pV = nRT

  p = pressure (Pa)

  V = volume (m3)

  n = moles (mol)

  R = gas constant (8.31 JK-1mol-1)

  T = temperature (K)
• how do you convert m3 to dm3?

  x 1000
• how do you convert dm3 to cm3?

  x 1000
• what do ionic equations show?


  the ions that are formed in solution and show which particles are reacting
• what is the empirical formula?

  the simplest whole number ratio of elements in a compound
• how do you work out empirical formula?

  1. write out the elements involved

  2. write the percentages as masses

  3. divide the relative atomic mass to get number of moles

  4. divide all the numbers by the smallest number of moles
• what is the equation for percentage yield?

  percentage yield = actual yield/theoretical yield x 100
• what is atom economy?


  How efficient a reaction is
• how do you workout atom economy?

  % atom economy = Mr of desired product / sum of Mr of all reactants x 100
• Why is atom economy important?

  - companies will try to use reactions that tend towards 100% atom economy

  - high atom economies means that raw materials are used more efficiently. this is more sustainable

  - high atom economies produce less waste and so benefit the environment

  - higher atom economy means less by-products so less time and money spent separating these from the desirable product