☜
Reagents 2

Reagents 2 — Calculating Final Concentrations

 
You are told what volume of stock solution of a component was added to a reaction mixture before adjusting to a final total volume. You are to calculate its final concentration.

Final conc: mM   
 
You should aim to do these calculations in your head or on a scrap of paper (i.e. without a calculator). The following logic may be helpful:
  • The stock solution becomes diluted when a specific added volume is included in a larger total volume.
  • The dilution is equal to the total volume divided by the volume of stock added.
  • One multiplies the concentration of stock by this dilution factor to get the final concentration.
  • The final concentration is therefore:
    (stock concentration x stock volume)/final volume
Always do a ‘sanity check’ on your answer. Is it the right order of magnitude? E.g. for a dilution factor of 8.5, round this up to 10 and check whether your answer is somewhere near one-tenth of the original concentration (rather than one-hundredth).