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Separation methods

Syllabus VWO: Chemical methods

Question 1 / 50 correct

Which method removes undissolved sand from salt water?

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More explanation and a worked example

Start with the desired product

A filter retains undissolved solid particles. Dissolved salt passes through an ordinary filter with the water. During evaporation the solvent leaves as vapour; it is not automatically collected.

Properties make the difference

Distillation uses differences in volatility and collects vapour after cooling. Extraction uses differences in solubility. Adsorption binds substances to a surface. Settling uses particles sinking under suitable conditions.

You have sand, dissolved salt and water. You want to recover dry salt.

  1. Filter: sand remains as residue, while salt solution passes through as filtrate.
  2. Evaporate the filtrate to recover the salt.
Want to collect water as well? Choose distillation after filtration.
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