Determination of the concentration of limewater solution in g dm-3 as accurately as possible against a standard solution of HCl acid

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PLAN

The aim of my investigation is to determine the concentration of limewater solution in g dm-3 as accurately as possible against a standard solution of HCl acid.

BACKGROUND INFORMATION ABOUT LIMEWATER

Limewater solution is a clear coloured saturated Ca(OH)2 produced when calcium carbonate (limestone) is decomposed to form calcium oxide CaO. Water is then added to form CaO (quicklime), to produce slaked lime. Again, excess water is added to form Ca(OH)2 , limewater. Limewater, which is an alkali is used principally in medicine as an antacid as a neutraliser for acidic poisoning or treatment of burns. Limewater as an alkali would have a pH scale of 9-14.

I am going to set up my equipment in the form of an acid/base titration since it is a way of measuring quantities of reactants and can be very useful in determining an unknown concentration or following the progress of a reaction which is related to my investigation. The reaction is between an acid (HCl) and alkali, (Ca (OH)2) and therefore it’s a neutralisation reaction.

In order to determine the concentration of limewater in an experimental way, it is very important to use the most appropriate equipment available. This is why I have chosen to use a pipette, volumetric flask and a burette, as they have an accuracy of +-0.005 cm3, which should produce a suitable accuracy for my experiment. The apparatus I am going to use in my experiment is;

  • Burette (50 cm3)
  • Pipette (5 cm3)
  • Beaker (250 cm3)
  • Measuring cylinder (100 cm3)
  • Volumetric flask (250 cm3)
  • Pipette filler
  • Funnel
  • Stand and Clamp
  • Conical flask (250 cm3)
  • White tile

I will be using a 250 cm3 volumetric flask as it is what is provided for my experiment and also it will ensure that my results is reliable because it is the exact volume needed to dilute the a HCl acid whereas if it was a much bigger volume we would have to measure 250 cm3 from that volume and this brings about errors.

WORKING OUT DILUTION OF HYDROCHLORIC ACID

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The hydrochloric acid provided has a concentration of 2.00 mol dm-3. This acid is too concentrated and therefore if it were to be used in a titration, a very small amount would need to be added in order to neutralise the calcium hydroxide. The end point would be reached too quickly and this will make it difficult to measure accurately the amount of acid needed for neutralisation and will therefore need to be diluted.

Balanced equation for my neutralisation reaction is;

Ca(OH)2 (aq) + 2HCl (aq)               CaCl2 (aq) + 2H2O (l)

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