Question

Which from following compounds is NOT in gaseous phase at \(25^\circ C\)?

• A. \(\mathrm{ClF}\)
• B. \(\mathrm{BrF}\)
• C. \(\mathrm{IF_3}\)
• D. \(\mathrm{ClF_3}\)

Hint:

Among interhalogen compounds, heavier molecules generally have higher melting and boiling points due to stronger van der Waals forces.

Answer 1

The Correct Option is C

Concept: The physical state of interhalogen compounds depends mainly on:
• Molecular mass
• Intermolecular forces
• Size of halogen atoms As molecular size and mass increase, intermolecular attraction becomes stronger, causing the compound to exist as liquid or solid at room temperature.

Step 1: Analyzing the given compounds.

• \(\mathrm{ClF}\) is a small interhalogen compound and exists as a gas.
• \(\mathrm{BrF}\) also exists in gaseous state near room temperature.
• \(\mathrm{ClF_3}\) is gaseous at room temperature.
• \(\mathrm{IF_3}\) contains heavy iodine atoms and stronger intermolecular forces.

Step 2: Identifying the non-gaseous compound.
Because of its larger molecular mass and stronger intermolecular attractions: \[ \mathrm{IF_3} \] exists as a solid at room temperature. Therefore, it is not gaseous at \(25^\circ C\). Hence, the correct answer is: \[ \boxed{(C)\ \mathrm{IF_3}} \]