Qualitative analysis
How to do salt analysis · Viva · Quiz
To analyse the given inorganic salt for one acidic and one basic radical.
| Experiment | Observation | Inference |
|---|---|---|
| Warm the solid salt with dilute H₂SO₄ | Brown fumes of NO₂ are evolved | NO₂⁻ may be present |
| Confirmatory Tests | ||
| Potassium Iodide Starch Test Take evolved gas and add KI + starch solution acidified with acetic acid | Blue colour appears | NO₂⁻ is confirmed |
| Sulphanilic Acid / 1-Naphthylamine Test Acidify 1 mL of water extract with acetic acid and add sulphanilic acid solution followed by 1-naphthylamine reagent | Red colour is formed | NO₂⁻ is confirmed |
| Experiment | Observation | Inference |
|---|---|---|
| Original solution + H₂S gas in presence of dil. HCl | Black precipitate of Group-II A is formed | Group-II cation may be present |
| Confirmatory Tests | ||
| Ammonium Hydroxide Test To the original solution (or the filtrate after dissolving the black ppt in dilute HNO₃) add NH₄OH dropwise, then in excess | Pale blue precipitate of Cu(OH)₂ dissolves in excess NH₄OH giving a deep blue tetraamminecopper(II) solution | Cu²⁺ is confirmed |
| Potassium Ferrocyanide Test Acidify the solution with acetic acid and add potassium ferrocyanide | Chocolate-brown precipitate of copper ferrocyanide | Presence of Cu²⁺ is confirmed |
The given salt contains Cu²⁺ as the cation (basic radical) and NO₂⁻ as the anion (acidic radical). The salt is Copper(II) Nitrite (Cu(NO₂)₂).