Question

Which of the following gas gives a dense white fumes when brought near a glass rod dipped in ammonia?
1. H₂
2. HCl
3. CO₂
4. SO₂

Answer 1

Correct Answer - Option 2 : HCl

Explanation:

• The gas which when brought near a glass rod dipped in ammonia gives dense white fumes is HCl.
• The reaction that takes place is:

NH₃ + HCl → NH₄Cl ( dense white fumes)

• The dense white fumes are due to the formation of gaseous Ammonium chloride NH₄Cl.

 

• HCl is a colorless, gas that is acidic in nature.
• HCl turns blue litmus paper red.
• SO₂ is also an acidic gas.
• The detection of SO₂ can be done by its reaction with lime water. It turns lime water milky due to the formation of Calcium Sulphite, a white insoluble precipitate.
• The reaction is:

Ca(OH)₂ + SO₂ → CaSO₃

• Similarly, CO2 also turns lime water milky.

Ca(OH)2 + CO2 → CaCO3

• H₂ burns with a pop sound.