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

Which of the following statements is incorrect?

An aqueous solution of a salt $X$ turns blood red on treatment with $CNS^{-}$ and blue on treatment with $K_4[Fe(CN)_6]$. $X$ also gives a positive chromyl chloride test. The salt $X$ is

$A$ mixture of $NaCl$ and $K_{2}Cr_{2}O_{7}$ is heated with conc. $H_{2}SO_{4}$,deep red vapours are formed. Which of the following statements is false?

Which of these reactions is correct?

The correct option$(s)$ to distinguish nitrate salts of $Mn^{2+}$ and $Cu^{2+}$ taken separately is (are):
$(A)$ $Mn^{2+}$ shows the characteristic green colour in the flame test
$(B)$ Only $Cu^{2+}$ shows the formation of precipitate by passing $H_2S$ in acidic medium
$(C)$ Only $Mn^{2+}$ shows the formation of precipitate by passing $H_2S$ in faintly basic medium
$(D)$ $Cu^{2+}/Cu$ has higher reduction potential than $Mn^{2+}/Mn$ (measured under similar conditions)