Question

Which is the correct decreasing order of boiling points for different compounds from following ?

• A. \(\text{CH}_3\text{Cl} > \text{CH}_3\text{Br} > \text{CH}_2\text{Br}_2 > \text{CHBr}_3\)
• B. \(\text{CH}_3\text{Br} > \text{CH}_2\text{Br}_2 > \text{CHBr}_3 > \text{CH}_3\text{Cl}\)
• C. \(\text{CH}_2\text{Br}_2 > \text{CHBr}_3 > \text{CH}_3\text{Br} > \text{CH}_3\text{Cl}\)
• D. \(\text{CHBr}_3 > \text{CH}_2\text{Br}_2 > \text{CH}_3\text{Br} > \text{CH}_3\text{Cl}\)

Hint:

Boiling point of similar haloalkanes rises with molecular mass and surface area, so more bromine atoms means a higher boiling point.

Answer 1

The Correct Option is D

Step 1: Idea
For related compounds, the one with more electrons and a bigger, softer electron cloud sticks to its neighbours more strongly and so needs more heat to boil.

Step 2: Ranking
CHBr3 has three Br atoms, CH2Br2 has two, CH3Br has one, and CH3Cl has one lighter Cl. So the order of intermolecular attraction is CHBr3 > CH2Br2 > CH3Br > CH3Cl.

Step 3: Check with data
Experimental values near 422 K, 370 K, 277 K and 249 K agree with this ranking.

Step 4: Reject the others
Orders that start with CH3Cl or CH3Br put a small molecule at the top, which reverses the effect of size. Option (D) is the only sequence that decreases all the way.

Final Answer:
The order follows molecular mass from highest to lowest. This is option (D). \[ \boxed{\text{(D) }\text{CHBr}_3 > \text{CH}_2\text{Br}_2 > \text{CH}_3\text{Br} > \text{CH}_3\text{Cl}} \]