Valence bond theory and crystal field theory — practice questions

Question 1 · difficulty L2 · understanding

The ratio of spin-only magnetic moment values $$\mu_{\text {eff }}\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{3-} / \mu_{\text {eff }}\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}$$ is _________.

Question 2 · difficulty L2 · understanding

For a metal ion, the calculated magnetic moment is $$4.90 ~\mathrm{BM}$$. This metal ion has ___________ number of unpaired electrons.

Question 3 · difficulty L2 · understanding

[Ti(H 2 O) 6 ] 3+ absorbs light of wavelength 498 nm during a d $$-$$ d transition. The octahedral splitting energy for the above complex is ____________ $$\times$$ 10 $$-$$19 J. (Round off to the Nearest Integer). h = 6.626 $$\times$$ 10 $$-$$34 Js; c = 3 $$\times$$ 10 8 ms $$-$$1

Question 4 · difficulty L2 · understanding

Given below are two statements: Statement I: Each electron in $\mathrm{e}_{\mathrm{g}}$ orbitals destabilizes the orbitals by $+0.6 \Delta_{\mathrm{o}}$ and each electron in the $t_{2 g}$ orbitals stabilizes the orbitals by $-0.4 \Delta_0$ in an octahedral field on the basis of crystal field theory. Statement II: All the d - orbitals of the transition metals have the same energy in their free atomic state but when a complex is formed the ligands destroy the degeneracy of these orbitals on the basis of crystal field theory. In the light of the above statements, choose the correct answer from the options given below

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Question 5 · difficulty L2 · understanding

$$\text { Match the LIST-I with LIST-II }$$ List-I Complex ion List-II Calculated spin only magnetic moment (BM) A. $$\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$$ I. 3.87 B. $$\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$$ II. 5.92 C. $$\left[\mathrm{Cu}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$$ III. 4.90 D. $$\left[\mathrm{Mn}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$$ IV. 1.73 Choose the correct answer from the options given below :

• A. A-I, B-III, C-IV, D-II
• B. A-II, B-I, C-III, D-IV
• C. A-IV, B-II, C-I, D-III
• D. A-III, B-I, C-IV, D-II

Question 6 · difficulty L2 · understanding

Match List - I with List - II. List - I Chromium (III) Complexes (en = ethylene diamine) List - II Δ₀ (cm⁻¹) A [Cr(CN)₆]³⁻ I. 15,060 B [CrF₆]³⁻ II. 17,400 C [Cr(H₂O)₆]³⁺ III. 22,300 D [Cr(en)₃]³⁺ IV. 26,600 Choose the correct answer from the options given below:

• A. A-I, B-II, C-III, D-IV
• B. A-II, B-III, C-IV, D-I
• C. A-III, B-IV, C-I, D-II
• D. A-IV, B-I, C-II, D-III

Question 7 · difficulty L2 · understanding

$$\text { Match the LIST-I with LIST-II }$$ LIST-I (Molecules/ion) LIST-II (Hybridisation of central atom) A. $$\mathrm{PF}_5$$ I $$\mathrm{dsp}^2$$ B $$\mathrm{SF}_6$$ II $$\mathrm{sp}^3 \mathrm{~d}$$ C $$\mathrm{Ni}(\mathrm{CO})_4$$ III $$\mathrm{sp}^3 \mathrm{~d}^2$$ D $$\left[\mathrm{PtCl}_4\right]^{2-}$$ IV $$\mathrm{sp}^3$$ $$\text { Choose the correct answer from the options given below: }$$

• A. A-IV, B-I, C-II, D-III
• B. A-III, B-I, C-IV, D-II
• C. A-II, B-III, C-IV, D-I
• D. A-I, B-II, C-III, D-IV

Question 8 · difficulty L2 · understanding

Given below are two statements : Statement (I) : In octahedral complexes, when $\Delta_0<\mathrm{P}$ high spin complexes are formed. When $\Delta_0>P$ low spin complexes are formed. Statement (II) : In tetrahedral complexes because of $\Delta_t < P$, low spin complexes are rarely formed. In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both Statement I and Statement II are incorrect
• B. Statement I is correct but Statement II is incorrect
• C. Statement I is incorrect but Statement II is correct
• D. Both Statement I and Statement II are correct

Question 9 · difficulty L2 · understanding

The correct order of ligands arranged in increasing field strength.

• A. $$\mathrm{F}^{-}<\mathrm{Br}^{-}<\mathrm{I}^{-}<\mathrm{NH}_3$$
• B. $$\mathrm{H}_2 \mathrm{O}<\mathrm{^{-}OH}<\mathrm{CN}^{-}<\mathrm{NH}_3$$
• C. $$\mathrm{Br}^{-}<\mathrm{F}^{-}<\mathrm{H}_2 \mathrm{O}<\mathrm{NH}_3$$
• D. $$\mathrm{Cl}^{-}<\mathrm{^{-}OH}<\mathrm{Br}^{-}<\mathrm{CN}^{-}$$

Question 10 · difficulty L2 · understanding

The correct sequence of ligands in the order of decreasing field strength is :

• A. $$\mathrm{NCS}^{-}>\mathrm{EDTA}^{4-}>\mathrm{CN}^{-}>\mathrm{CO}$$
• B. $$\mathrm{CO}>\mathrm{H}_2 \mathrm{O}>\mathrm{F}^{-}>\mathrm{S}^{2-}$$
• C. $$\mathrm{S}^{2-}>{ }^{-} \mathrm{OH}>\mathrm{EDTA}^{4-}>\mathrm{CO}$$
• D. $${ }^{-} \mathrm{OH}>\mathrm{F}^{-}>\mathrm{NH}_3>\mathrm{CN}^{-}$$