Question

Which among the following compounds is NOT a colourless gas?

• A. ClF
• B. $\text{IF}_7$
• C. $\text{IF}_3$
• D. $\text{ClF}_3$

Hint:

As a general trend in p-block chemistry, iodine-containing compounds with lower fluorine ratios (like $\text{IF}_3$ or ICl) tend to exhibit solid states and distinct dark or vibrant colors (yellows, browns, purples) due to the large, easily polarizable electron cloud of the heavy Iodine atom.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
We must identify which interhalogen compound listed is not a colorless gas at room temperature.

Step 2: Key Formula or Approach:
The physical state and color of interhalogens depend on the elements involved and molecular weight, with lighter, highly symmetric molecules typically being colorless gases.

Step 3: Detailed Explanation:
ClF, IF₇, and ClF₃ are all known to exist as colorless gases under standard ambient conditions. In contrast, IF₃ is unstable at room temperature and exists as a bright yellow solid, thus it is not a colorless gas.

Step 4: Final Answer:
The compound that is not a colorless gas is IF₃, which corresponds to option (C).