Qualitative Analysis

The student adds aqueous chlorine to W and concludes that W contains iodide ions.

Describe the observation that the student makes that leads to this conclusion.

Explain how this shows that W contains iodide ions.

observation ______

explanation ______

Describe another test and the observation that confirms that W contains iodide ions.

test ______

observation ______

The student does a flame test on W and observes a lilac flame.

Describe how the student does the flame test on W.

______

Identify W.

______

X contains one anion and one cation.

The student:

• adds aqueous sodium hydroxide to X in a test-tube
• warms the mixture
• holds a piece of damp red litmus paper above the test-tube.

A white precipitate, soluble in excess aqueous sodium hydroxide, is formed.

The litmus paper does not change colour.

State three conclusions that are made from these observations.

______

The conclusions in (d) identify cations that may be present in X.

Describe another test that the student does and its observations to identify the cation in X.

test ______

observations ______

The student adds excess aqueous sodium hydroxide to X, then adds a piece of aluminium foil and warms the mixture.

Ammonia gas is given off and tested with damp red litmus paper.

Describe what happens to the litmus paper.

______

Identify the anion in X.

______

Predict the identity of the gas produced in test 1.

Describe how the student tests the gas to confirm its identity.

gas ______
test and observation ______

The solution produced in test 1 contains an anion.

Name a reagent that reacts with this anion to form a white precipitate when added to the solution produced in test 1 after the addition of dilute nitric acid.

______

The observations for test 3 are incomplete.

State one other observation the student makes in test 3.

______

Solid $\mathbf{Y}$ contains only one cation. The student cannot identify the cation from the observations in Table 3.1.

Use Table 3.1 to name the two cations which could be present in $\mathbf{Y}$.

______

Describe an additional test the student does on the solution produced in test 1 to identify the cation in $\mathbf{Y}$.

______

The student adds aqueous sodium hydroxide to $\mathbf{Z}$ in a boiling tube.

Describe how the student completes this test to identify the cation in $\mathbf{Z}$.

______

The student adds dilute nitric acid and then aqueous silver nitrate to $\mathbf{Z}$.

A precipitate is formed. It is difficult to tell if the precipitate is white or cream in colour.

Describe how the student uses separate aqueous solutions of a chloride and a bromide to decide the colour of the precipitate.

______

The student adds dilute nitric acid and then aqueous barium nitrate to $\mathbf{Z}$.

Predict the expected observation.

______

Complete the table with the expected observations.

Identify X.

______

Complete the table with the expected observations.

Identify X.

______

Ammonium sulfite, $(\text{NH}_4)_2\text{SO}_3$, is a water-soluble compound.

Aqueous ammonium sulfite is slowly oxidised by oxygen in air.

This means aqueous ammonium sulfite will also contain some sulfate ions, $\text{SO}_4^{2-}$.

Describe a series of tests, and the observations, to show the presence of ammonium ions, sulfite ions and sulfate ions in this solution.

It must be clear in your answer which ion is identified by each test.

Calcium ammonium nitrate, $\text{CaNH}_4(\text{NO}_3)_3$, is a water-soluble compound.

Describe a series of tests, and the observations, to identify the calcium, ammonium and nitrate ions in a sample of $\text{CaNH}_4(\text{NO}_3)_3$.

Your description will need to explain how to prevent ammonium ions interfering with the test for nitrate ions.