1. Tardigrade
  2. Question
  3. Chemistry
  4. Pick out the correct statements from the following 1. Cobalt (III) is more stable in octahedral complexes 2. Zinc forms coloured ions or complexes 3. Most of the d-block elements and their compounds are ferromagnetic 4. Osmium shows (VIII) oxidation state 5. Cobalt (II) is more stable in octahedral complexes

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Q. Pick out the correct statements from the following
1. Cobalt $(III)$ is more stable in octahedral complexes
2. Zinc forms coloured ions or complexes
3. Most of the d-block elements and their compounds are ferromagnetic
4. Osmium shows $(VIII)$ oxidation state
5. Cobalt $(II)$ is more stable in octahedral complexes

KEAMKEAM 2008Coordination Compounds

Solution:

1. $ C{{o}^{3+}} $ have higher charge density than $ C{{o}^{2+}} $ so $ C{{o}^{3+}} $ is more stable in octahedral complexes.
2. Zn exhibits only +2 oxidation state. So
$ Z{{n}^{2+}}=[Ar]\,3{{d}^{10}},4{{s}^{0}} $
Since it does not contain any unpaired electron, its compounds are colorless.
3. d-block elements are generally paramagnetic and sometimes, but not ferromagnetic
4. Osmium and ruthenium are VIII group elements, so can exhibit the highest oxidation state +8 in their oxides, eg, $ Os{{O}_{4}} $ .
Hence, statement 1 and 4 are correct.