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The salt that reacts with dilute hydrochloric acid to produce a pungent smelling gas which...

Chemistry
JAMB 2018

The salt that reacts with dilute hydrochloric acid to produce a pungent smelling gas which decolourizes acidified purple potassium tetraoxomanganate (VII) solution is

  • A. Na\(_2\)SO\(_4\)
  • B. Na\(_2\)SO\(_3\)
  • C. Na\(_2\)S
  • D. Na\(_2\)CO\(_3\)
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Correct Answer: Option B
Explanation

When sodium sulphite (Na₂SO₃) reacts with hydrochloric acid (HCl), it produces sulphur dioxide gas (SO₂), which readily decolourises acidified potassium permanganate (KMnO₄) solution. 

Reaction: Na₂SO₃(aq) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + SO₂(g) 

The reaction produces sodium chloride (NaCl), water (H₂O), and sulphur dioxide gas (SO₂). Sulphur dioxide gas (SO₂) is a reducing agent, and when it reacts with acidified potassium permanganate (KMnO₄), it decolourises the purple solution. 

There is an explanation video available below.


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