In the flame test of a mixture of salts,a green flame with a blue centre was observed. Which one of the following cations may be present?

Which pair of cations can be identified by the borax bead test?

While preparing crystals of Mohr's salt,dil. $H_2SO_4$ is added to a mixture of ferrous sulphate and ammonium sulphate,before dissolving this mixture in water,dil. $H_2SO_4$ is added here to:

Identify the technique used to know the binding nature of nanomaterials.

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$2KI + FeCl_2 \longrightarrow$ No reaction

On performing a borax-bead test with a given inorganic mixture for qualitative analysis,the colour of the bead was found to be emerald green both in oxidising and reducing flame. It indicates the possibility of the presence of