Match List I with List II
| List I | List II |
| A. Phosphine | I. Catches fire in air |
| B. Chlorine water | II. Smoke screen |
| C. White phosphorus | III. Crown structure |
| D. Sulphur monoclinic and rhombic | IV. Bleaching agent |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-II, B-IV, C-I, D-III
(A) Phosphine — This matches (II) Smoke screen. Calcium phosphide in water gives phosphine, which catches fire spontaneously; this is used in Holme’s signals and in smoke screens:
\( \ce{Ca3P2 + 6H2O -> 3Ca(OH)2 + 2PH3} \)
(B) Chlorine water — This matches (IV) Bleaching agent. Chlorine in water gives nascent oxygen, which oxidises coloured matter; the bleaching is permanent:
\( \ce{Cl2 + H2O -> 2HCl + [O]} \)
(C) White phosphorus — This matches (I) Catches fire in air. The \( \ce{P4} \) molecule has strained 60° bond angles, so white phosphorus is very reactive and burns in air, giving dense white fumes:
\( \ce{P4 + 5O2 -> P4O10} \)
(D) Sulphur monoclinic and rhombic — This matches (III) Crown structure. Both forms contain \( \ce{S8} \) molecules, and the \( \ce{S8} \) ring is puckered with a crown shape.
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.