| 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 |
A) 1 and 2
B) 1 and 3
C) 2 and 4
D) 1 and 4
E) 2 and 5
Correct Answer: D
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.
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