The determination of the solubility of calcium hydroxide.

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Aim

The experiment practical I am going to do is all about the determination of the solubility of calcium hydroxide. This can be found by titrating the saturated solution against a solution of an acid whose concentration you know. The acid whose concentration we know is hydrochloric acid. The calcium hydroxide will be in limewater and this will have to be diluted before used. These two solutions will react together and a colour change will occur. Calcium hydroxide dissolves only slightly in water to form an alkali solution.

Introduction

A titration is when two solutions react together. It is a technique to find the concentration of unknown solution. It is a method of quantitative analysis. One solution, which has a known concentration, is filled into a burette and the second solution is placed in a conical flask. A solution of known concentration or known morality is called a standard solution. In each titration the solution with the unknown concentration is filled in the burette is added in small measured quantities to the solution in the conical flask until just enough has been added for the reaction to be complete. The solution in the conical flask will have a fixed volume to start with until the solution in the burette is added to it and a visible colour change has occurred which means the two solutions have reacted together. Often an indicator is added to show when the reaction is finished to show the end point of a titration between an acid and an alkali an indicator can normally be used. The indicator can show when the base has been neutralised completely. Different indicators are suitable for different concentrations of strong and weak acids and alkali such as:

  • For a titration between a strong acid and a weak alkali = methyl orange is used as an indicator.
  • For a titration between a weak acid and strong alkali = phenolphthalein is used as an indicator.
  • For a titration between a strong acid and strong alkali = methyl orange or phenolphthalein is used.
  • For a titration between a weak acid and a weak alkali no indicator is suitable = a pH meter, conductivity meter or temperature probe has to be used.

 An analysis involving a titration is sometimes called a volumetric analysis. Titration’s have to be very accurate.

A concentration is a measure of the amount of substance in a given volume of solution typically measured in mol dm.

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Calcium hydroxide (Ca(OH)

In water calcium hydroxide form alkali solution, although they are not very soluble. Hydroxides can react with acids to form salts. A neutralising effect is used by farmers when they put lime- calcium hydroxide- on their field to neutralise soil acidity. This is done as if the soil is too acidic, most crops will not grow well.

Hydrochloric acid (HCL)

Hydrochloric acid is a strong acid. Hydrochloric acid is used to break our food into smaller molecules in our stomach. As it is a strong acid it has a much higher electrical ...

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