Qualitative Analysis: Tests for Ions Practice Questions

Give the colour of the flame produced by each of these ions.

lithium ion, $\mathrm{Li^+}$ .......................................................

copper ion, $\mathrm{Cu^{2+}}$ .......................................................

Describe how to carry out a flame test on a solid compound.

One of the solids produces an orange-red flame.

Name the metal ion present in this solid.

Complete the table to give the colour of the precipitate formed in each case.

solution	colour of precipitate
copper(II) sulfate
iron(II) sulfate
iron(III) sulfate

A fourth solution forms a white precipitate when a few drops of sodium hydroxide solution are added. The precipitate dissolves to form a colourless solution when excess sodium hydroxide solution is added.

Name the metal ion in this solution.

Name the reagent that should be added to the solid in tube 1.

Name liquid Y and state what would be observed in tube 2 if the solid contains carbonate ions.

A flame test on the solid produces a yellow flame.

Use this result and the result of the test in tube 2 to name the solid.

Describe a test to show that the solution contains sulfate ions.

Give the result of a positive test.

Give the reason why dilute hydrochloric acid is added before the barium chloride solution.

Write the ionic equation for the formation of the white precipitate.

Describe how to test a solution for halide ions.

Complete the table to give the colour of the precipitate formed with each solution.

solution	colour of precipitate
sodium chloride
sodium bromide
sodium iodide

Silver nitrate solution is harmful and stains the skin.

Give one safety precaution, other than wearing eye protection, that should be taken when carrying out this test.

Describe how a student could show that the fertiliser contains ammonium ions.

Give the result of a positive test.

Explain why a chemical test used to identify an ion must be unique to that ion.

State what the student would see when a few drops of sodium hydroxide solution are added to each solution.

Describe how the student could use sodium hydroxide solution to distinguish between solution A and solution B.

Write the ionic equation for the formation of the precipitate in solution A.

The sample of mineral water gives a meter reading of 35.

Determine the concentration of potassium ions in the mineral water.

Give the unit.

Give two advantages of using a flame photometer rather than a flame test to analyse this sample.

A second sample gives a meter reading of 84.

Give the reason why the concentration of potassium ions in this sample cannot be found reliably from these results.

Identify the two metal ions present in the sample.

Explain why the flame test did not show that both of these ions were present.

Name salt A.

Name salt B.

Name salt C and explain how the test results identify each of its ions.

Explain why the result of the sodium hydroxide test on salt A does not, by itself, show that potassium ions are present.

A student is given a solution of a single salt. The student is asked to find out whether the salt contains chloride ions or sulfate ions.

This is the student's method.

Step 1 Add dilute hydrochloric acid to a sample of the solution, then add silver nitrate solution. A white precipitate forms. The student concludes that chloride ions are present.

Step 2 Add barium chloride solution to a second sample of the solution. A white precipitate forms. The student concludes that sulfate ions are also present.

Evaluate the student's method and conclusions, and describe the changes needed to obtain valid results.