SC14- quantitative analysis

• theoretical yield is the mass of product we should get in a reaction.

  amount of product you actually get is the actual yield.

  percentage yield compares the two and is calculated by this equation:

  percentage yield = actual/theoretical x 100
• yield is never 100% for three main reasons:

  1. reaction may be incomplete as it is not left for long enough
  2. some product may be lost when transferring from one container to another
  3. there may be unwanted side reactions
• atom economy is the percentage of reactants that are converted to a useful product.

  it can be calculated by this equation:

  atom economy = mr of useful product/mr of all products x 100

  when deciding which reaction to use, raw materials, atom economy, energy consumption, rate of reaction and purity of product should be used.
• concentration of a solution tells us how much of a substance is dissolved in water.

  the equation for concentration is:

  mass (or mols) / volume

  the units for concentration is g/dm(3)

  to convert from cm(3) to dm(3), you must divide by a thousand.
• making a standard solution (titration to calculate concentration of an unknown solution) :

  • use mass balance to measure base
  • dissolve solute in small amount of solvent
  • transfer solution to volumetric flask- piece of glassware that measures one volume
  • rinse beaker with deionised water and add rinsings to volumetric flask, this ensures all of the solution has been added
  • add water dropwise and fill until the bottom of the meniscus sits on the line
  • stopper and shake/invert flask to mix contents and ensure solute is dissolved.
• only concordant results; results within 0.5cm3 of each other are included in the mean.
• we can calculate the amount of mols in a gas by the volume.

  we use the formula:

  moles = volume / 24

  24 is the molar volume- volume occupied by 1 mol of any gas at room temperature and pressure.