technique?
Filter off the sand [1]. Sand is solid but copper(II) sulfate is in solution [1].
To chose the best method to purify a substance from a mixture you have to know the following properties of the different substances in the mixture:
You then need to separate the component of the solution. Distillation is appropriate because water has a low boiling point and copper(II) sulfate has a high boiling point.
• state at room temperature and pressure • solubility in water or other solvent • differences in boiling points Mixture requiring separation
Separation method
insoluble solid and liquid crystals of solid from a solution two soluble solids with different solubility in water and organic solvent a volatile liquid from a solution of a non-volatile solid a mixture of liquids with different boiling points
filtration crystallisation using an organic solvent and separating funnel
The filtrate is a solution of copper(II) sulfate [1]. This is distilled [1]. The copper(II) sulfate remains in the flask [1] because it has a high boiling point [1]. The water condenses in the condenser and is collected as a distillate [1]. NOTE: simple distillation is used rather than crystallisation, because purified water was required.
simple distillation
Progress check
fractional distillation
3.07 What is the best method to separate water from aqueous copper(II) sulfate? [1]
Table 3.02
Unit 3 Methods of purification
3.08 Which purification
3.08 Hexane and octane are liquids with slightly different boiling points. Suggest the best method of separating these liquids. [1]
Worked example 3.02
3.09 What is the simplest method of separating powdered chalk from water? [1]
Describe how you would separate a mixture of sand and aqueous copper(II) sulfate to obtain purified sand, copper(II) sulfate and water. Give an explanation for each stage you use. [7]
3.10 What is the best method of separating two dyes with different solubility in water? [1]
In order to choose the correct method of separation you need to know the solubility of each component, for example sand is insoluble in water and copper(II) sulfate is soluble in water. So the first step is to separate the solid from the solution.
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