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JEE Advanced Unit 2A: Chemical Bonding, Lewis Diagrams & Molecular Geometry — practice questions

Explore 3 free Unit 2A: Chemical Bonding, Lewis Diagrams & Molecular Geometry questions in JEE Advanced Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Unit 2A: Chemical Bonding, Lewis Diagrams & Molecular Geometry questions and exercises with answers

Showing questions 1–3 of 3.

Among HF, HCl, HBr, HI: order of bond ENTHALPY (strength):Read the answer and worked solution →Effective nuclear charge (Z_eff) felt by an electron in 2p orbital of nitrogen, given Z = 7, screening constant σ ≈ 3.25:Read the answer and worked solution →Among NaCl, NaBr, NaI: order of melting points:Read the answer and worked solution →

Worked practice questions

Among HF, HCl, HBr, HI: order of bond ENTHALPY (strength):

  1. All equal
  2. HF > HCl > HBr > HI
  3. HCl > HF > HBr > HI
  4. HI > HBr > HCl > HF
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Correct answer: B. HF > HCl > HBr > HI

As we go down the halogen group, bond length increases (atom size grows), so bond becomes WEAKER. So HF (shortest, strongest) > HCl > HBr > HI (longest, weakest). This is also why HI is the strongest acid in water (easiest to dissociate).

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Effective nuclear charge (Z_eff) felt by an electron in 2p orbital of nitrogen, given Z = 7, screening constant σ ≈ 3.25:

  1. ~7
  2. ~1.85
  3. ~3.75
  4. ~5.75
Show answer and solution

Correct answer: C. ~3.75

Z_eff = Z - σ = 7 - 3.25 ≈ 3.75. Slater's rules give the approximate effective charge after accounting for shielding by inner electrons.

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Among NaCl, NaBr, NaI: order of melting points:

  1. NaI > NaBr > NaCl
  2. NaCl > NaBr > NaI (smaller anion = stronger lattice)
  3. All equal
  4. NaBr > NaCl > NaI
Show answer and solution

Correct answer: B. NaCl > NaBr > NaI (smaller anion = stronger lattice)

As anion size grows (Cl⁻ < Br⁻ < I⁻), inter-ionic distance r grows, lattice energy ∝ 1/r decreases. **Hence melting point decreases:** NaCl (801°C) > NaBr (747°C) > NaI (661°C).

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