CAIE IGCSE Chemistry Qualitative Analysis Tests

Practise selecting reagents and observations for anions, aqueous cations, gases and flame tests across qualitative analysis questions.

Exam points

identify anions by adding the stated reagent and recording the required precipitate or colour change
identify aqueous cations from precipitate colour and behaviour with excess sodium hydroxide or ammonia
identify gases and metal ions using litmus, splints, limewater, potassium manganate(VII) or flame colours

Covered syllabus points

12.5.1—Anion tests 12.5.2—Cation tests using aqueous sodium 12.5.3—Gas tests: NH3 with damp red litmus 12.5.4—Use of a flame test to identify the

[Maximum number: 6]

Concentrated ammonia solution gives off ammonia gas. Concentrated hydrochloric acid gives off hydrogen chloride gas. Ammonia, $\mathrm{NH}_{3}$ , and hydrogen chloride, HCl , are both colourless gases. Ammonia reacts with hydrogen chloride to make the white solid ammonium chloride.

Apparatus is set up as shown.

Figure for Question 12.5 Identification of ions and gases question 1 — CAIE IGCSE Chemistry

After ten minutes a white solid forms in the tube where the gases meet.

(a)

Some of the white solid is removed from the tube and dissolved in water.

Describe how the white solid could be tested to show it contains,

[ 6 ]

(i)

ammonium ions,
test
result

[ 3 ]

(ii)

chloride ions.
test
result

[ 3 ]

[Maximum number: 2]

Hydrogen can be manufactured from methane by steam reforming.

\mathrm{CH}_{4}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{~g}) \rightleftharpoons \mathrm{CO}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g})

The reaction is carried out using a nickel catalyst at temperatures between $700^{\circ} \mathrm{C}$ and $1100^{\circ} \mathrm{C}$ and using a pressure of one atmosphere.

The forward reaction is endothermic.

Hydrogen can also be manufactured by electrolysis. The electrolyte is concentrated aqueous sodium chloride. The electrodes are inert.

The products of electrolysis are hydrogen, chlorine and sodium hydroxide.

Describe a test for chlorine.
test
result

All question bank results loaded

Covered syllabus points

12.5 Identification of ions and gases question 1

Question (a)

Question (i)

Question (ii)

12.5 Identification of ions and gases question 2