Question

The treatment of galena with $HNO _3$ produces a gas that is

• A. paramagnetic
• B. bent in geometry
• C. an acidic oxide
• D. colorless

Answer 1

The Correct Option is A, D

The reaction of galena (PbS) with nitric acid (HNO₃) produces sulfur dioxide (SO₂) as the gas. The reaction is as follows:

\(\text{PbS} + 2\text{HNO}_3 \rightarrow \text{Pb(NO}_3)_2 + \text{SO}_2 + \text{H}_2\text{O}\)

The gas produced is sulfur dioxide (SO₂), which is a colorless gas with a pungent odor.

Now, let's analyze the properties of sulfur dioxide (SO₂), the gas produced during this reaction:

• Paramagnetic: Sulfur dioxide (SO₂) is paramagnetic because it has an unpaired electron in its molecular orbital, which causes it to be attracted by a magnetic field. SO₂ has a bent molecular geometry and contains an odd number of electrons.
• Bent in Geometry: The molecular geometry of SO₂ is bent due to the lone pairs of electrons on the sulfur atom, which causes repulsion. However, this does not directly relate to the gas properties as described in the options.
• Acidic Oxide: SO₂ is an acidic oxide because it reacts with water to form sulfurous acid (H₂SO₃). While this is true, the question primarily asks about the properties of the gas produced, which is sulfur dioxide.
• Colorless: SO₂ is colorless under standard conditions, making it a colorless gas.

Now, let's evaluate the given options:

• Option A: "Paramagnetic" – This is correct because SO₂ is paramagnetic due to its unpaired electron.
• Option B: "Bent in geometry" – This is incorrect because while SO₂ has bent geometry, the focus of the question is on the gas properties, not its molecular geometry.
• Option C: "An acidic oxide" – While SO₂ is indeed an acidic oxide, the primary focus of the question is on the gas properties (paramagnetic and colorless).
• Option D: "Colorless" – This is correct because SO₂ is a colorless gas under standard conditions.

Final Answer: The correct options are: A and D.