Chemistry - Complete d-block Question with Solution | TestHub

A. Copper(II) sulfate reacts with excess potassium cyanide to form a colorless complex, $[Cu(CN{)}_4{]}^{3-}$.

B. Fe²⁺ is oxidized to Fe³⁺ (yellow solution) by MnO₄⁻ (purple) in acidic medium, which is reduced to Mn²⁺ (colorless).

C. Cobalt(III) is unstable in aqueous solution and is reduced to Co(II) unless stabilized by strong field ligands.

D. In AgO, Ag has oxidation states +1 and +3. In CuO, Cu has oxidation state +2.

The final answer is $\boxed{A,B}$