When a salt is treated with sodium hydroxide solution,it gives gas $X$. On passing gas $X$ through reagent $Y$,a brown-coloured precipitate is formed. $X$ and $Y$ respectively,are

$A$ is:
$\text{Salt } A \text{ (Colourless)} \xrightarrow{Cu} \text{Blue solution}$
$\text{Salt } A \text{ (Colourless)} \xrightarrow{HCl_{(aq)}} \text{White ppt}$
$\text{Salt } A \text{ (Colourless)} \xrightarrow{\text{Conc. } H_2SO_4} \text{Brown fumes}$

$A$ metal salt solution forms a yellow precipitate with potassium chromate in acetic acid,a white precipitate with dilute $H_2SO_4$,but gives no precipitate with $NaCl$. The metal salt solution will consist of:

Which of the following statement$(s)$ is/are correct with reference to $Fe^{2+}$ and $Fe^{3+}$ ions?
$(1)$ $Fe^{3+}$ gives brown colour with potassium ferricyanide
$(2)$ $Fe^{2+}$ gives blue colour with potassium ferricyanide
$(3)$ $Fe^{3+}$ gives red colour with potassium thiocyanate
$(4)$ $Fe^{2+}$ gives brown colour with ammonium thiocyanate

The yellow precipitate formed during the chromyl chloride test is chemically

Formation of which complex,among the following,is not a confirmatory test of $Pb^{2+}$ ions?