Tests for cations for IGCSE and O Level Chemistry

A solution containing a certain cation produces a white precipitate when a few drops of sodium hydroxide are added. This precipitate then dissolves when excess sodium hydroxide is added. Which cation is it?

• Calcium ion (Ca²⁺)

• Aluminum ion (Al³⁺)

• Sodium ion (Na⁺)

• Iron(II) ion (Fe²⁺)

Which pair of cations can be distinguished by observing their reactions with excess sodium hydroxide, given that both form a precipitate with a few drops of sodium hydroxide?

• Aluminum ion (Al³⁺) and Zinc ion (Zn²⁺)

• Calcium ion (Ca²⁺) and Lead(II) ion (Pb²⁺)

• Aluminum ion (Al³⁺) and Calcium ion (Ca²⁺)

• Iron(II) ion (Fe²⁺) and Iron(III) ion (Fe³⁺)

A solution containing a certain cation produces a white precipitate when a few drops of ammonia are added. This precipitate then dissolves when excess ammonia is added. Which cation is it?

• Aluminum ion (Al³⁺)

• Lead(II) ion (Pb²⁺)

• Zinc ion (Zn²⁺)

• Calcium ion (Ca²⁺)

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Which metal ion's hydroxide precipitate dissolves in excess sodium hydroxide?

• Cu2+

• Fe2+

• Fe3+

• Cr3+

Which metal ion's hydroxide precipitate dissolves in excess ammonia?

• Cu2+

• Fe2+

• Fe3+

• Cr3+