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Chemistry · 2026 · 3 marks
CBSE 2026 · Region 3 · Set 1 · Q25
(a) Answer the following questions about the complexes [ NiCl_4]^2- and [ Ni ( CN )_4]^2- (i) Write the hybridization involved in each case. (ii)…
Answer the following questions about the complexes\[\left[\mathrm{NiCl}_{4}\right]^{2-} \text { and }\left[\mathrm{Ni}(\mathrm{CN})_{4}\right]^{2-} \]
(i)
Write the hybridization involved in each case.
(ii)
Which of them is the inner orbital complex and which one is the outer orbital complex ?
(iii)
Compare their magnetic behaviour. [Atomic number : Ni = $\displaystyle 28$]
(i)
Name two coordination compounds which are important in biological systems.
(ii)
What is meant by chelate effect? Give an example.
(iii)
Why are low spin tetrahedral complexes rarely formed?
Marking-scheme solution
(a)(i)
sp
$\displaystyle 3$, dsp
(ii)
[NiCl4]
$\displaystyle 2$- : outer orbital complex
[Ni(CN)$\displaystyle 4$]
$\displaystyle 2$- : inner orbital complex
(iii)
[NiCl4]
$\displaystyle 2$- : Paramagnetic
[Ni(CN)$\displaystyle 4$]
$\displaystyle 2$- : Diamagnetic
OR
(b)(i)
Haemoglobin, chlorophyll, vitamin B12 , Carboxypeptidase A,
Carbonic anhydrase
(ii)
Formation of stable complexes by di or polydentate ligand with
single metal atom/ ion.
[Pt(en)2Cl2]
$\displaystyle 2$-/ [Co(en)$\displaystyle 3$]
$\displaystyle 3$-
(iii) Because of low crystal field splitting energy or Δt < P
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