The document discusses qualitative analysis, which is a process chemists use to identify unknown substances. It involves performing chemical tests to determine the cations and anions present, allowing identification of the substance. Common tests include observing the appearance of solids and solutions, determining solubility, observing gases produced from heating or adding acids/alkalis. Gases can be identified using tests like their reaction with litmus, ability to relight a glowing splint, or forming precipitates with reagents. The goal is to perform experiments and make inferences to identify an unknown salt or mixture.

4. APPEARANCE OF SOLID 1. black powder 1. copper(II) oxide, charcoal 2. green powder 2. copper(II) carbonate 3. silvery/grey powder 3. metal 4 . pale green crystals 4. iron(II) salts 5. yellow/brown crystals 5. iron(III) salts 6. blue crystals 6. copper(II) salts

5. APPEARANCE OF SOLUTION 1. orange 1. dichromate ions 2. pale green 2. iron(II) ions 3. yellow 3. iron(III) ions chromate ions 4. brown 4. iron(III) ions iodine 5. blue 5. copper(II) ions

8. APPEARANCE OF RESIDUE AFTER HEATING 1. black solid 1. copper(II) oxide 2. yellow when hot, white when cold 2. zinc oxide 3. orange when hot, yellow when cold 3. lead(II) oxide 4. white solid sublimes 4. ammonium salt

10. GASES THAT CAN BE FORMED ON HEATING A SOLID 1. carbon dioxide 1. from carbonates 2. oxygen gas 2. from nitrates and certain oxides 3. ammonia 3. ammonium salts 4. reddish brown nitrogen dioxide gas 4. from nitrates

11. GASES THAT CAN BE FORMED ON REACTING A SOLID WITH ACID 1. carbon dioxide 1. from carbonates 2. hydrogen 2. from certain metals 3.sulphur dioxide 3. from sulphites