$A \xrightarrow{ K_4[Fe(CN)_6] } \text{Blue-white precipitate}$. Which ion is $A$?

Identify ions $A$ and $B$,respectively,based on the following reaction scheme:

Which of the following statement$(s)$ is(are) correct with reference to the ferrous and ferric ions?

Which of the following gives a black precipitate when $H_2S$ gas is passed through its solution?

$A$ salt '$A$' which gives a green flame with a Bunsen burner,on reaction with dil. $H_2SO_4$ produces gas $(2)$ and white turbidity $(Z)$. The saturated solution of gas $(2)$ on reaction with $H_2S$ gas produces '$Z$'. Then select the $CORRECT$ statement.

Which reagent is used in the qualitative analysis of Group $IV$ cations?