To Determine The Concentration Of A Limewater Solution

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To Determine The Concentration Of A Limewater Solution.

Aim: To determine the concentration of a limewater solution using hydrochloric acid of a known concentration of 2.00 moldm-3.

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

This shows that the reactants react in a 1:2 ratio.

This will be carried out using a titration.

However, as the concentration of the calcium hydroxide in the limewater is approximately 1g dm-3 and the concentration of the hydrochloric acid is 2.00moldm-3 the concentration of the hydrochloric acid needs to be reduced.

This can be done by a dilution.

To make the colour change in the titration distinct and so you know straight away when the solution has been neutralised phenolphthalein indicator will be used, as suggested in Understanding Chemistry.

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Safety: HCl is high in concentration and so could be irritant.

Lab coat and safety goggles must be worn.

Apparatus List:

For dilution:

  • Graduated pipette (5cm-3)
  • 250cm3 volumetric flask.
  • Distilled Water.
  • HCl solution.

For titration:

  • Graduated Pipette (25cm3)
  • Burette, Stand and Clamp
  • Funnel
  • Beaker containing 0.02moldm-3 HCl solution.
  • Beaker containing limewater of unknown concentration.
  • Conical Flask
  • Phenolphthalein Indicator & White Tile

Preparations: To work out the number of moles we can use the ‘n=m/M’ equation.

Concentration of Ca(OH)2(aq).

1g dm-3 approximately.

M of Ca(OH)2(aq) = 40 ...

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