To determine the presence of anion and cation in the given salt
| Experiment | Observation | Inference |
|---|---|---|
| Add conc. H₂SO₄ to the solution and boil with a few copper turnings/chips | On heating, brown fumes (NO₂) are evolved in excess and the solution becomes blue | NO₃⁻ may be present |
| Confirmatory Test | ||
| Brown Ring Test Take 1 mL of salt solution, add 2 mL conc. H₂SO₄, cool, then add freshly prepared ferrous sulphate solution along the sides | Brown ring is formed at the junction of the two solutions | NO₃⁻ is confirmed |
| Experiment | Observation | Inference |
|---|---|---|
| Original solution + NH₄OH solution | Reddish-brown precipitate | Group-III cation may be present |
| Confirmatory Tests | ||
| Potassium Ferrocyanide Test Dissolve the precipitate in dilute HCl, divide into two parts and add potassium ferrocyanide to one part | Blue/Prussian blue precipitate | Fe³⁺ is confirmed |
| Potassium Thiocyanate Test To second part add potassium thiocyanate solution | Blood-red colouration is formed | Fe³⁺ is confirmed |
The given salt contains Fe³⁺ ions as cation and NO₃⁻ ions as anion. The salt is Fe(NO₃)₃.