Ppt1 Introduction To Qa & Tests For Gases

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Ppt1 Introduction To Qa & Tests For Gases

  1. 1. What is Qualitative Analysis? <ul><li>It is a process that chemist carries out to identify an unknown. </li></ul><ul><li>This is done by finding out the CATIONs and ANIONs present in the unknown substance using chemcal tests that is, if the cation is Fe 2+ , anion is CO 3 2- , then the unknown substance is Iron(II) Carbonate, FeCO 3 . </li></ul>
  2. 2. QUALITATIVE ANALYSIS - Practical Examination <ul><li>The main purpose is to </li></ul><ul><li>test your ability to carry out simple experiments </li></ul><ul><li>record correct observations </li></ul><ul><li>infer from observations </li></ul><ul><li>The unknown substance is usually a salt or a mixture which may contain a cation or 2 anions. </li></ul>
  3. 3. Procedures involved in identification <ul><li>Procedure 1 </li></ul><ul><li>Preliminary Observation </li></ul><ul><li>-Appearance of unknown </li></ul><ul><li>The appearance of the unknown in its solid form or in solution often provides a clue to the detection of the unknown . </li></ul><ul><li>1. appearance of solid (colour) </li></ul><ul><li>2. appearance of aqueous solution (colour) </li></ul><ul><li>3. solubility of the unknown </li></ul>
  4. 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. 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
  6. 6. SOLUBILITY OF UNKNOWN(SALTS) <ul><li>1. nitrates </li></ul><ul><li>2. chlorides </li></ul><ul><li>3. sulphates </li></ul><ul><li>4. hydroxides & carbonates </li></ul>all are soluble all are soluble except PbCl 2 , AgCl all are soluble except PbSO 4 , BaSO 4 , CaSO 4 all are insoluble except for the Na + , K + & NH 4 + salt
  7. 7. Procedure 2 <ul><li>Dry Test(heating) </li></ul><ul><li>Useful detection about the identity of an unknown substance can be made from the results of heating a solid </li></ul><ul><li>By identifying the gas evolved </li></ul><ul><li>By observing the colour of residue </li></ul>
  8. 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
  9. 9. IDENTIFICATION OF GASES/ Test for gases <ul><li>Gases and vapours liberated during dry heating or by the addition of reagents such as acids or alkalis provides a clue on anions like CO 3 2- , NO 3 - and cation NH 4 + . </li></ul>
  10. 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. 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
  12. 12. IDENTIFICATION OF GASES CAN BE DONE BY THE FOLLOWING TESTS <ul><li>Ammonia NH 3 </li></ul><ul><li>Hydrogen H 2 , </li></ul><ul><li>Oxygen O 2 </li></ul><ul><li>Carbon dioxide CO 2 </li></ul><ul><li>Chlorine Cl 2 , </li></ul><ul><li>Sulphur dioxide SO 2 </li></ul>turns moist red litmus blue extinguishes lighted splint with “pop” sound relights glowing splint forms white ppt with limewater bleaches litmus paper turns orange potassium dichromate paper green

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