COMEDK 2024 Shift 2 Paper

The correct answer is Option A: A & C .
Let's analyze each statement:
A. Co2+ is easily oxidised to Co3+ in the presence of a strong ligand like CN−
This statement is correct. Here's why:
Cobalt(II) (Co2+) has a d7 electronic configuration, making it relatively stable. However, the presence of a strong ligand like cyanide (CN−)can significantly alter its stability.
Strong field ligands like cyanide cause a large crystal field splitting, leading to a low-spin configuration for Co2+. This low-spin configuration has all the electrons paired up in the lower energy d orbitals. The pairing of electrons in the d orbitals makes the oxidation of Co2+ to Co3+ ( d6 configuration) more favorable due to the increased stability of the low-spin d6 configuration in the presence of the strong field ligand.
B. [Fe(CN)6]4− is an octahedral complex ion which is paramagnetic in nature.
This statement is incorrect. Here's why:
The complex ion [Fe(CN)6]4− is indeed octahedral, but it is diamagnetic, not paramagnetic. Iron(II) (Fe2+) has a d6 electronic configuration. Cyanide (CN−), being a strong field ligand, causes a large crystal field splitting, resulting in a low-spin configuration.
In the low-spin configuration, all six electrons in the d orbitals are paired, making the complex diamagnetic (no unpaired electrons).
C. Removal of H2O molecules from [Ti(H2O)6]Cl3 on strong heating converts it to a colourless compound. square
This statement is correct. Here's why:
The complex [Ti(H2O)6]Cl3 is colored because the d orbitals of titanium(III) (Ti3+) are split by the ligand field, allowing for d-d electronic transitions that absorb certain wavelengths of light, resulting in a color.
Strong heating removes the water molecules, leading to the formation of anhydrous titanium(III) chloride (TiCl3).
Anhydrous titanium(III) chloride is colorless because in the absence of water ligands, the d orbitals are no longer split, and d-d transitions are not possible, meaning no light is absorbed.
D. Crystal Field splitting in Octahedral and Tetrahedral complexes is given by the equation
∆0=4∕9∆t
This statement is incorrect. Here's why:
The correct relationship between the crystal field splitting in octahedral (∆0) and tetrahedral (∆t) complexes is: ∆t=(4∕9)∆0.
This means that the crystal field splitting in tetrahedral complexes is approximately four-ninths of the splitting in octahedral complexes.
The reason for this difference is the geometric arrangement of the ligands. In an octahedral complex, the ligands are arranged at 90 degrees to each other, resulting in a stronger interaction with the metal d orbitals. In a tetrahedral complex, the ligands are at 109.5 degrees to each other, leading to a weaker interaction with the d orbitals.
In conclusion, the correct statements are A and C, explaining the oxidation behavior of cobalt in the presence of strong ligands and the color change associated with the dehydration of titanium(III) complexes.