The ions present in ionic compounds can be identified using simple tests.
Table 1 shows the flame test colours for four cations.
Table 1
| Cation | Flame test colour |
|---|---|
| barium | pale green |
| copper | blue-green |
| potassium | lilac |
| thallium | pale green |
Table 2 shows the results of three tests used to identify anions in solution.
Table 2
| Anion | Dilute nitric acid added | Barium chloride solution added | Bromothymol blue added |
|---|---|---|---|
| bromide | no change | no change | green |
| carbonate | effervescence | white precipitate | blue |
| hydrogensulfate | no change | no change | yellow |
| sulfate | no change | white precipitate | green |
| sulfite | effervescence | white precipitate | yellow |
Use the information in the tables to answer these questions.
In the tests, compound A gives a lilac flame and produces no change when barium chloride solution is added.
Suggest two possible identities for compound A.
In the tests, compound B gives a pale green flame and produces a white precipitate when barium chloride solution is added.
A student concludes that compound B is barium sulfate.
Give two reasons why this conclusion may not be correct.
Which additional test from Table 2 would show whether the anion in compound B is sulfate or carbonate?
An aqueous solution contains either bromide ions or hydrogensulfate ions.
Using only information from the tables, explain how you could decide if the solution contains bromide or hydrogensulfate ions.
35 exam-style questions on Edexcel IGCSE Chemistry Chemical tests. Each one has a worked solution and a mark scheme showing where the marks go.