Question:medium
Give one relevant observation for the following:
(a) Sodium hydroxide is added dropwise to Calcium nitrate solution.
(b) Dilute Hydrochloric acid is added to Iron (II) sulphide.
(c) An amphoteric metal is added to hot concentrated alkali.
Give one relevant observation for the following:
(a) Sodium hydroxide is added dropwise to Calcium nitrate solution.
(b) Dilute Hydrochloric acid is added to Iron (II) sulphide.
(c) An amphoteric metal is added to hot concentrated alkali.
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To distinguish between Calcium and Magnesium salts using NaOH: Calcium forms a white precipitate that is sparingly soluble, whereas Magnesium forms a white precipitate that remains strictly insoluble in excess NaOH!
Updated On: Mar 25, 2026
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Solution and Explanation
(a) Sodium hydroxide is added dropwise to Calcium nitrate solution:
A white precipitate of calcium hydroxide is formed.
The precipitate is slightly soluble in excess sodium hydroxide.
(b) Dilute Hydrochloric acid is added to Iron (II) sulphide:
A gas with a rotten egg smell (hydrogen sulphide gas, H2S) is evolved.
The gas is colourless but has a characteristic unpleasant odour.
(c) An amphoteric metal is added to hot concentrated alkali:
Hydrogen gas is evolved with brisk effervescence.
The metal dissolves forming a complex salt (such as sodium aluminate or zincate).
Final Observations:
(a) White precipitate formed
(b) Rotten egg smelling gas evolved
(c) Hydrogen gas evolved with effervescence
A white precipitate of calcium hydroxide is formed.
The precipitate is slightly soluble in excess sodium hydroxide.
(b) Dilute Hydrochloric acid is added to Iron (II) sulphide:
A gas with a rotten egg smell (hydrogen sulphide gas, H2S) is evolved.
The gas is colourless but has a characteristic unpleasant odour.
(c) An amphoteric metal is added to hot concentrated alkali:
Hydrogen gas is evolved with brisk effervescence.
The metal dissolves forming a complex salt (such as sodium aluminate or zincate).
Final Observations:
(a) White precipitate formed
(b) Rotten egg smelling gas evolved
(c) Hydrogen gas evolved with effervescence
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