$A$ solution of a salt in dilute sulphuric acid imparts a deep blue colour with starch-iodine solution; it confirms the presence of which of the following?

An anion solution gives a white precipitate with $AgNO_3$ solution. The precipitate dissolves in dilute ammonia due to the formation of:

Sodium salt solution $+ \, AgNO_3$ solution $\to$ Coloured precipitate: If the coloured precipitate is soluble in both dilute $HNO_3$ and excess concentrated $NH_3$ solution,then which of the following anions is present in the salt solution?

Explain the brown ring test for nitrate ions.

To an inorganic mixture,dilute $H_2SO_4$ is added in the cold; a colourless,odourless gas is evolved. The mixture contains:

The salt which responds to dilute and concentrated $H_2SO_4$ is