Which of the following is soluble in yellow ammonium sulphide?

Find the compound $A$ from the following reaction sequences:
$A$ $\xrightarrow{\text{aqua-regia}} B$ $\xrightarrow[(2) CH_3COOH]{(1) KNO_2 \mid NH_4OH} \text{yellow ppt}$

Conc. $HNO_3$ is added before proceeding to test for group $III$ members. This is to

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

Which of the following compounds will not give a positive chromyl chloride test?

In the analysis of Group-$II$ basic radicals,$H_2S$ gas is passed in the presence of dilute $HCl$ because...