Let's analyze both Assertion A and Reason R:
Assertion A: In \( \text{Ni(CO)}_4 \) and \( \text{Fe(CO)}_5 \), the carbonyl ligand (\( \text{CO} \)) is neutral. Thus, the oxidation state of Ni and Fe in these complexes is indeed zero. So, Assertion A is correct.
Reason R: Low oxidation states of metals are stabilized by synergistic bonding, also known as backbonding. This involves σ-donation from the ligand to the metal and π-backdonation from the metal to the ligand. Crucially, the ligand must have empty π orbitals to accept electrons from the metal. \( \text{CO} \) is a π-acceptor ligand, not a π-donor ligand. So, Reason R is incorrect.
The correct answer is (3): A is correct, but R is not correct.
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)

Cobalt chloride when dissolved in water forms pink colored complex $X$ which has octahedral geometry. This solution on treating with cone $HCl$ forms deep blue complex, $\underline{Y}$ which has a $\underline{Z}$ geometry $X, Y$ and $Z$, respectively, are

What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)
A black body is at a temperature of 2880 K. The energy of radiation emitted by this body with wavelength between 499 nm and 500 nm is U1, between 999 nm and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien's constant, b = 2.88×106 nm-K. Then,