The table shows how to tell apart two colourless solutions, sodium chloride and sodium sulfate. Which test gives a different result for the two solutions? t...
Question 1 Report
The table shows how to tell apart two colourless solutions, sodium chloride and sodium sulfate. Which test gives a different result for the two solutions?
| test | sodium chloride | sodium sulfate |
| flame test | yellow | yellow |
| acidified barium nitrate | no precipitate | white precipitate |
Answer Details
Compare the two columns row by row. The flame test gives yellow for both solutions, because both contain sodium ions, so it cannot separate them. Acidified barium nitrate gives no precipitate with sodium chloride but a white precipitate with sodium sulfate, so that is the test that tells them apart.
The white solid is insoluble barium sulfate: \( \mathrm{Ba^{2+} + SO_4^{2-} \rightarrow BaSO_4} \). The dilute nitric acid is added first to destroy any carbonate ions, which would also give a white precipitate.
Limewater is a test for a gas, and both solutions are close to neutral, so measuring pH would not distinguish them either.
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