1. Silver salts dissolve readily in 3 M HNO₃ due to the formation of a soluble complex. When silver salts, such as silver chloride (AgCl), are added to a solution of 3 M HNO₃, the nitrate ions (NO₃⁻) from the HNO₃ react with the silver ions (Ag⁺) from the silver salt to form a soluble complex called silver nitrate (AgNO₃). This complex is soluble in water, allowing the silver ions to dissociate and remain in solution.
2. Fresh chlorine water is critical for testing group II anions because it helps identify the presence of chloride ions (Cl⁻). In the presence of chloride ions, chlorine water (Cl₂ dissolved in water) reacts with the chloride ions to form a yellow precipitate of silver chloride (AgCl). This reaction is used as a confirmatory test for chloride ions.
By adding fresh chlorine water to a solution containing group II anions (such as sulfates, carbonates, or sulfides), the formation of a yellow precipitate indicates the presence of chloride ions, helping to identify the specific group II anion present. The fresh chlorine water is important because if it is not fresh, it may contain other impurities or chlorine-consuming substances that can interfere with the test and produce inaccurate results.
In summary, silver salts dissolve readily in 3 M HNO₃ due to the formation of a soluble complex with nitrate ions. Fresh chlorine water is critical for testing group II anions as it helps identify the presence of chloride ions by forming a yellow precipitate of silver chloride.