Answer the question on basis of passage given below:
P block elements are placed in groups 13 to 18 of the periodic table. Their valence shell electronic configuration is \(ns^2\, \ np^{1-6}\). Group 16 of the p-block elements are known as the group of chalcogens having \(ns^2\, \ np^4\) as their general electronic configuration. They exhibit number of oxidation states but the stability of \(-2\) oxidation state decreases down the group. They are sometimes also known as group of chalcogens as the name is derived from the Greek word for brass and points to the association of sulphur and its congeners with copper. Their ionization enthalpy decreases down the group. Oxygen shows anomalous behaviour due to its small size and high electronegativity.
What will be the products formed in the following equation?
\(U (s) + 3ClF_3 (l) \longrightarrow _{------} + _{------}\)
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → UF6(g) and 3ClF(g)
\( \ce{ClF3} \) is an interhalogen compound and a powerful fluorinating agent. It fluorinates uranium to its highest oxidation state, +6, giving volatile \( \ce{UF6} \), the compound used in the enrichment of 235U. Chlorine is reduced from +3 in \( \ce{ClF3} \) to +1 in ClF:
\( \displaystyle \ce{U(s) + 3ClF3(l) -> UF6(g) + 3ClF(g)} \)
Atom check: U 1 = 1; Cl 3 = 3; F 9 = 6 + 3, so the equation balances.
Why the other options are incorrect
Option (1) UF4(g) and 3UCl(g) — Incorrect. It needs four uranium atoms on the right but only one is present on the left, and only 4 of the 9 fluorine atoms are accounted for; no UCl is formed.
Option (3) UF4(g) and 3ClF(g) — Incorrect. The right side has only 4 + 3 = 7 fluorine atoms against 9 on the left, so it does not balance; \( \ce{ClF3} \) takes uranium to \( \ce{UF6} \), not \( \ce{UF4} \).
Option (4) UF6(g) and 3UCl(g) — Incorrect. \( \ce{UF6} \) is right, but uranium does not form UCl here; the three chlorine atoms leave as ClF, and this side would have four uranium atoms.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Uses – “… Interhalogen compounds are very useful fluorinating agents. ClF3 and BrF3 are used for the production of UF6 in the enrichment of 235U.
U(s) + 3ClF3(l) → UF6(g) + 3ClF(g)”