The formation of Prussian blue color by ferric ions is due to the formation of which compound?

Which ligand is useful for the removal of the toxic effect of lead metal in the body during chelate therapy treatment?

In photography,sodium thiosulphate is used as:

Identify $(A)$ to $(E)$ and also explain the reactions involved.
$CuCO_3 \to CuO$ $\xrightarrow{\text{Heat with } CuS} (A)$ $\xrightarrow{\text{conc. } HNO_3} (B)$ $\xrightarrow{NH_{3(aq)}} (C) \text{ (Blue solution)}$
$CuCO_3 \to (D)$ $\xrightarrow{Ca(OH)_2} (E) \text{ (Milky)}$ $\xrightarrow{CO_2} Ca(HCO_3)_2 \text{ (Clear solution)}$

The complex formed by carbon monoxide with hemoglobin is called .....

Wilkinson's catalyst is used in