Chemistry 5070 · O Level · Identification of ions and gases

Identification of ions and gases — practice question

A student examines solution $\textbf{X}$ and solution $\textbf{Y}$. Both solutions are colourless. (a) The student carries out some tests on $\textbf{X}$. Table 3.1 records the observations the student notes for these tests.
(a(i))[1]

One step in the method for test $1$ is missing. Describe the missing step in the method that is needed to produce the observations shown.

(a(ii))[1]

The observations for test $1$ are not complete. State one additional observation made in test $1$.

(a(iii))[1]

Suggest why the ammonia produced in test $2$ does not affect the litmus paper.

(a(iv))[1]

Solution $\textbf{X}$ contains two cations. Identify the cation in solution $\textbf{X}$ that produces ammonia in test $2$.

(a(v))[2]

Explain why the student cannot identify the second cation in solution $\textbf{X}$ from the tests and observations in Table 3.1.

(a(vi))[1]

Identify the anion in $\textbf{X}$.

(b(i))[1]

The student places universal indicator into solution $\textbf{Y}$ in a test-tube. The universal indicator becomes red. Identify the cation present in $\textbf{Y}$.

(b(ii))[2]

The student puts a piece of magnesium ribbon into $\textbf{Y}$. Hydrogen is given off. Suggest two observations the student makes.

(b(iii))[2]

Describe how the student tests the gas to show that it is hydrogen. test ........................................... observation if hydrogen present ...........................................

(c(i))[1]

The student adds dilute nitric acid, then aqueous silver nitrate, to $\textbf{Y}$. A white precipitate is seen. Identify the anion present in $\textbf{Y}$.

(c(ii))[1]

Identify $\textbf{Y}$.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: An excess of (aqueous) sodium hydroxide was added

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