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Testing for Ions

2017 Paper One

Question Eight
Part of a series looking at past AQA A-level Chemistry questions with a focus on better performance in examinations.

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AQA A-level CHEMISTRY Paper 1 Inorganic and Physical ChemistryTuesday 13 June 2017

6-mark question on ion identification

Add a barium chloride or barium hydroxide solution to each.
For potassium nitrate, there would be no visible changeFor potassium sulfate, a white precipitate will form.
There's a double displacement reaction between barium chloride and potassium sulfate.
Potassium chloride (soluble) and barium sulfate (insoluble) are formed.
The barium sulfate precipitates out of the solution

Here, the reagent will be sodium hydroxide (in fact, any Group 1 hydroxide)
Add sodium hydroxide solution to both solutions
For magnesium chloride, you get a white precipitate. The precipitate will not dissolve in excess sodium hydroxide.
A white precipitate also forms from the aluminium chloride solution.
The precipitate will dissolve in excess sodium hydroxide

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