JEE Main · 2025 · Shift-ImediumMOLE-228

Which of the following statement is true with respect to H2O, NH3 and CH4? A. The central atoms of all the molecules…

Some Basic Concepts (Mole Concept) · Class 11 · JEE Main Previous Year Question

Question

Which of the following statement is true with respect to H2O\text{H}_2\text{O}, NH3\text{NH}_3 and CH4\text{CH}_4?

A. The central atoms of all the molecules are sp3sp^3 hybridized. B. The H–O–H, H–N–H and H–C–H angles in the above molecules are 104.5°104.5°, 107.5°107.5° and 109.5°109.5° respectively. C. The increasing order of dipole moment is CH4<NH3<H2O\text{CH}_4 < \text{NH}_3 < \text{H}_2\text{O}. D. Both H2O\text{H}_2\text{O} and NH3\text{NH}_3 are Lewis acids and CH4\text{CH}_4 is a Lewis base. E. A solution of NH3\text{NH}_3 in H2O\text{H}_2\text{O} is basic. In this solution NH3\text{NH}_3 and H2O\text{H}_2\text{O} act as Lowry-Bronsted acid and base respectively.

(a) A and E Only \quad (b) D and E Only \quad (c) A, D and E Only \quad (d) A, B and C Only

Options
  1. a

    A and E Only

  2. b

    D and E Only

  3. c

    A, D and E Only

  4. d

    A, B and C Only

    ✓
Correct Answerd

A, B and C Only

Detailed Solution

🧠 Same hybridisation, different lone pairs \ceCH4\ce{CH4}, \ceNH3\ce{NH3} and \ceH2O\ce{H2O} all have sp3sp^3 hybridisation on the central atom. The difference is the lone-pair count: 0,1,20, 1, 2. Each extra lone pair squeezes the bond angle smaller and shifts the polarity.

🗺️ Check each statement

  • (A) All three centres have 44 electron pairs (bond + lone) → sp3sp^3. True.
  • (B) Bond angles: \ceCH4\ce{CH4} 109.5°109.5°, \ceNH3\ce{NH3} 107.5°107.5°, \ceH2O\ce{H2O} 104.5°104.5°. Each lone pair pushes the bonds closer. True.
  • (C) Dipole moments: \ceCH4\ce{CH4} (00 D, symmetric) < \ceNH3\ce{NH3} (1.471.47 D) < \ceH2O\ce{H2O} (1.851.85 D). True.
  • (D) \ceH2O\ce{H2O} and \ceNH3\ce{NH3} have lone pairs to donate — they are Lewis bases, not acids. False.
  • (E) In aqueous \ceNH3\ce{NH3}: \ceNH3\ce{NH3} accepts a proton (base), \ceH2O\ce{H2O} donates one (acid). The roles given in the statement are swapped. False.

So A, B, C are true → option (d).

⚠️ Common mistake Many students mark (a) thinking statement E is correct. Read carefully — the statement assigns acid/base roles backwards. \ceNH3\ce{NH3} is the base here, not the acid.

Answer: (d)\boxed{\text{Answer: (d)}}

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