Chemistry MCQs for NEET — Practice Questions with Answers

$Co^{2+}$ ions typically exhibit a pink color in their hydrated form, and $Mn^{2+}$ ions are also known to be pale pink. Therefore, the correct option is $Co^{2+}$ and $Mn^{2+}$, which match the description of having a pink color.

$Ti^{3+}$ ions are known to exhibit a purple color. This is due to the specific electronic transitions within the d-orbitals of the titanium ion, which absorb certain wavelengths of light and reflect the purple color.

The color of hydrated salts is due to the d-d transitions of the metal ions in the crystal field created by the water molecules. Here are the correct matches:

1. $NiCl_2 ullet 6H_2O$ is green
2. $Co(NO_3)_2 ullet 6H_2O$ is pink
3. $FeCl_3$ is yellow
4. $CuSO_4 ullet 5H_2O$ is blue

Therefore, the correct matching is 1-d, 2-a, 3-e, 4-c.

In the contact process for the production of sulfuric acid, $V_2O_5$ (vanadium pentoxide) is used as the catalyst to convert $SO_2$ to $SO_3$. The reaction is as follows:

$$2SO_2 + O_2 ightarrow 2SO_3$$

This reaction is catalyzed by $V_2O_5$.

The magnetic moment can be calculated using the same formula: $$ ext{Magnetic Moment} ( ext{BM}) = ext{n(n+2)} $$, where 'n' is the number of unpaired electrons. For $Fe^{2+}$ in $FeSO_4$, which has an electron configuration of [Ar] 3d^6, there are 4 unpaired electrons. Therefore, the magnetic moment is approximately 4.90 BM.

Transition metal ions are known to form complex compounds due to their small size, high nuclear charge, and the presence of different oxidation states. However, the statement 'Co-ordination covalent bond is not directional' is incorrect. Co-ordination bonds are indeed directional, as the geometry of the complex depends on the spatial arrangement of the ligands around the central metal ion.

To prepare alloys, the difference in atomic radii of the constituent elements should be less than 15%. This rule helps ensure that the alloy has a homogeneous structure and maintains good mechanical properties. If the atomic radii difference is too large, it can lead to structural inconsistencies and weaken the alloy.