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How to Develop a Set of Solubility Rules

Solubility rules are developed in Chemistry to indicate compounds that can be mixed and separate them from those that are immiscible. Substances that are insoluble form a precipitate when mixed in the same volumes. In some cases, the solubility rules are used to classify the compounds in categories, such as slightly soluble, insoluble or soluble. Insoluble substances are defined by the fact that they form a precipitate when mixed. The rules are created from set reactions used to assess the solubility of the compounds. This is followed by a critical analysis of the changes and observations made during the experiment. There are various general principles and steps that are followed in order to come up with the rules.

Things You'll Need

Data table
Chemicals
Solubility chart
Reagents

Instructions

- 1
  Select the compounds under study in accordance to the various classes as identified in their chemical composition. For instance, separate the sulphates, hydroxides, nitrates and phosphates.
- 2
  Mix the respective compounds that are to be tested. This should be accompanied by a fill-out of the substances under test in a data table. A data table provides details for future reference.
- 3
  Test the substances for solubility by adding reagents to the mixture above. Ensure that the compounds are in equal proportions to obtain accurate results.
- 4
  Observe and record the changes that occur on addition of the reagents. These should be categorized as insoluble, soluble and unknown. Record each observation in its own space to allow ease of analysis.
- 5
  Fill out the solubility chart as the final record of solubility. This clearly indicates the soluble compounds as well as the insoluble.
- 6
  Analyze the data to come up with concrete rules of solubility such as all ammonium salts are soluble. Analysis of the solubility rules help in providing helps in identifying which reagents are soluble. A simple and straightforward criterion is used in analyzing solubility of the compounds.
- 7
  Record any exceptions to the observed rules with respect to the categories of the compounds. Exceptions to solubility rules defined may be needed by changes in the properties of the reagents if you observe several factors. These include changes in temperature as well as concentration of the reagents in the mixture.

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