Crystal field theory, colour and magnetic properties
- Which of the following are paramagnetic?A. [NiCl_4]^2- B. Ni(CO)_4 C. [Ni(CN)_4]^2- D. [Ni(H_2O)_6]^2+ E. Ni(PPh_3)_4Choose the correct answer from the options given below: Answer: 3. A and D only Key idea: paramagnetic means unpaired electrons. A: mathrm[NiCl₄]²⁻ , mathrmNi²⁺ d⁸, weak field Cl⁻, tetrahedral sp³... 1
- The correct order of the wavelength of light absorbed by the following complexes is,A. [Co(NH_3)_6]^3+ B. [Co(CN)_6]^3- C. [Cu(H_2O)_4]^2+ D. [Ti(H_2O)_6]^3+Choose the correct answer from the options given below: Answer: 2. B < A < D < C Key idea: the larger the crystal field splitting Δ , the higher the energy absorbed and the shorter the wavelength.... 1
- The order of energy absorbed which is responsible for the color of complexes(A) [Ni(H_2O)_2(en)_2]^2+(B) [Ni(H_2O)_4(en)]^2+ and(C) [Ni(en)_3]^2+is Answer: 4. (C) > (A) > (B) Key idea: stronger field ligands cause larger splitting Δ_o , so the complex absorbs higher energy light. Ligand... 1
- Match List - I with List - II.List - I : (a) [Fe(CN)_6]^3- (b) [Fe(H_2O)_6]^3+ (c) [Fe(CN)_6]^4- (d) [Fe(H_2O)_6]^2+List - II : (i) 5.92 BM (ii) 0 BM (iii) 4.90 BM (iv) 1.73 BMChoose the correct answer from the options given below. Answer: 4. (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii) Key idea: find unpaired electrons n and use μ=√(n(n+2)) BM. (a) mathrm[Fe(CN)₆]³⁻ : mathrm... 1
- Which of the following is the correct order of increasing field strength of ligands to form coordination compounds ? Answer: 1. SCN ^- < F ^- < C ₂ O ₄²⁻ < CN ^- From the spectrochemical series (weak to strong field): mathrmI^- So the increasing order is ma... 1
- What is the correct electronic configuration of the central atom in K_4[Fe(CN)_6] based on crystal field theory ? Answer: 2. t_2g⁶e_g⁰ In K₄[Fe(CN)₆] iron is Fe(II), a d⁶ ion. CN^- is a strong field ligand, so the pairing energy is lower than Δ_o and all... 1
- Which one of the following ions exhibits d-d transition and paramagnetism as well ? Answer: 4. MnO ₄²⁻ d-d transitions need partly filled d orbitals; paramagnetism needs unpaired electrons. mathrmCrO₄²⁻ : Cr(+6), d⁰ . MnO₄^-... 1
- Match the metal ions given in Column I with the spin magnetic moments of the ions given in Column II and assign the correct code :Column I: a. Co^3+; b. Cr^3+; c. Fe^3+; d. Ni^2+Column II: i. √(8) B.M.; ii. √(35) B.M.; iii. √(3) B.M.; iv. √(24) B.M.;… Answer: 1. a-iv, b-v, c-ii, d-i Use μ=√(n(n+2)) with n unpaired electrons. mathrmCo³⁺ ( d⁶ , high spin, n = 4): √(24) (iv). mathrmCr³⁺ ( d³... 1
- Correct increasing order for the wavelengths of absorption in the visible region for the complexes of Co^3+ is : Answer: 4. [Co(en)₃]³⁺, [Co(NH₃)₆]³⁺, [Co(H₂O)₆]³⁺ Key idea: stronger ligand field means a larger splitting Δ_o , which means light of highe... 1
- Jahn-Teller effect is not observed in high spin complexes of Answer: 1. d⁸ Key idea: Jahn-Teller distortion occurs when the e_g or t_2g set is unevenly filled (degenerate ground state). High spin d⁸ :... 1