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CAIE IGCSE Chemistry 12.5 Identification of Ions and Gases Questions

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

Syllabus
2026–2028
Course
Chemistry 0620

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 tests12.5.2—Cation tests using aqueous sodium12.5.3—Gas tests: NH3 with damp red litmus12.5.4—Use of a flame test to identify the

Question 1

[Maximum number: 1]

When acid is added to salt X, a gas is produced which turns limewater milky.
When sodium hydroxide is added to salt X, a gas is produced which turns litmus paper blue.
What is X ?

A

CaCO3\mathrm{CaCO}_{3}

B

(NH4)2CO3\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}

C

NH4NO3\mathrm{NH}_{4} \mathrm{NO}_{3}

D

ZnCO3\mathrm{ZnCO}_{3}

Question 2

[Maximum number: 1]

Which gas is produced when ammonium chloride is warmed with aqueous sodium hydroxide?

A

ammonia

B

chlorine

C

hydrogen

D

nitrogen

Question 3

[Maximum number: 2]

When iron(II) sulfate crystals are heated strongly, sulfur dioxide gas is given off.

Describe a test for sulfur dioxide gas.
test
observations

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