To determine the presence of anion and cation in the given salt
| Experiment | Observation | Inference |
|---|---|---|
| Take 0.1 g of salt and add conc. H₂SO₄ | A colourless gas is evolved which gives dense white fumes with ammonia | Cl⁻ may be present |
| Confirmatory Tests | ||
| Concentrated H₂SO₄ and MnO₂ Test Take a pinch of MnO₂ in salt solution and add 3–4 drops of conc. H₂SO₄, then heat | Greenish yellow chlorine gas is evolved | Presence of Cl⁻ is indicated |
| Silver Nitrate Test Acidify 1 mL of sodium carbonate extract with dilute HNO₃ (or use water extract) and add AgNO₃ solution | Curdy white precipitate soluble in NH₄OH | Cl⁻ is confirmed |
| Chromyl Chloride Test Take a little salt with solid K₂Cr₂O₇, add conc. H₂SO₄, heat. Pass the evolved gas through sodium hydroxide solution, divide into two parts. Acidify one part with acetic acid and add lead acetate solution | The sodium hydroxide solution becomes yellow; adding acetic acid and lead acetate gives yellow precipitate of lead chromate | Cl⁻ is confirmed |
| Experiment | Observation | Inference |
|---|---|---|
| Original solution + H₂S gas in presence of NH₄OH | Black precipitate is formed | Group IV cation may be present |
| Dissolve the black sulphide precipitate in aqua regia and heat | Residue remains in solution after evaporation | Co²⁺ may be present |
| Confirmatory Test | ||
| Potassium Hexanitritocobaltate(III) Test Neutralise with NH₄OH, acidify with dilute acetic acid and add strong potassium nitrite solution | Yellow precipitate is formed | Presence of Co²⁺ is confirmed |
The given salt contains Co²⁺ ions as cation and Cl⁻ ions as anion. The salt is Co(Cl)₂.