What are the acid–base nature and structure of SO₂?
▶️ Answer/Explanation
Ans: B
Sulfur dioxide (\(SO_2\)) is an acidic gas with a bent (V-shaped) molecular structure. The sulfur atom is \(sp^2\) hybridized, forming two sigma bonds with oxygen atoms and retaining one lone pair, giving a bond angle of approximately \(119^\circ\). In aqueous solution, \(SO_2\) dissolves to form sulfurous acid (\(H_2SO_3\)), confirming its acidic nature.
Which statement is correct?
▶️ Answer/Explanation
Ans: A
Hydrogen bromide (HBr) acts as a reducing agent and reacts with concentrated sulfuric acid (H2SO4) to produce sulfur dioxide (SO2), bromine (Br2), and water. This confirms statement A as correct. The other options are incorrect because: (B) HBr decomposes at a lower temperature than HCl, (C) AgBr is a cream precipitate (not yellow), and (D) HBr cannot decolorize iodine solution.
Which statement correctly describes what happens when silicon tetrachloride is added to water?
▶️ Answer/Explanation
Ans: C
When silicon tetrachloride (SiCl₄) is added to water, it undergoes hydrolysis:
\[ \text{SiCl}_4 + 2\text{H}_2\text{O} \rightarrow \text{SiO}_2 \downarrow + 4\text{HCl} \]
This reaction produces:
- Silicon dioxide (SiO₂) as a white precipitate.
- Hydrochloric acid (HCl), making the solution acidic.
Thus, the correct description is C (a precipitate and an acidic solution).
Consider the following four compounds.
1 (CH₃)₃CH
2 CH₃CH₂CH₂OH
3 CH₃CH₂CH₂SH
4 CH₃CH₂CH₂CH₃
What is the order of increasing boiling point of the compounds (lowest first)?
A. 1 → 4 → 2 → 3
B. 1 → 4 → 3 → 2
C. 4 → 1 → 2 → 3
D. 4 → 1 → 3 → 2
▶️ Answer/Explanation
Ans: B
The boiling points depend on intermolecular forces. 1 (CH₃)₃CH (branched alkane) and 4 CH₃CH₂CH₂CH₃ (linear alkane) have the weakest London dispersion forces, with 1 having a lower boiling point due to branching. 3 CH₃CH₂CH₂SH (thiol) has stronger dipole-dipole interactions than alkanes but weaker than hydrogen bonds in 2 CH₃CH₂CH₂OH (alcohol). Thus, the correct order is 1 → 4 → 3 → 2.