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SS3: CHEMISTRY - 1ST TERM

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  1. Volumetric Analysis (Titration) | Week 1
    3 Topics
    |
    1 Quiz
  2. Heat of Neutralization & Redox Titrations | Week 2
    2 Topics
    |
    1 Quiz
  3. Test for Common Gases | Week 3
    1 Topic
  4. Qualitative Analysis I | Week 4
    2 Topics
  5. Qualitative Analysis II | Week 5
    1 Topic
  6. Qualitative Analysis III | Week 6
    2 Topics
  7. Qualitative Analysis IV - Anions | Week 7
    1 Topic
  8. Test for Fat and Oil; Protein; Starch | Week 8
    3 Topics
  9. Petroleum I | Week 9
    4 Topics
    |
    1 Quiz
  10. Petroleum II | Week 10
    4 Topics
    |
    1 Quiz



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Gases are identified using their properties. Properties such as colour, odour, combustibility, action on litmus paper, and so on are the common properties used to identify gases. The table below summarizes the common gases and key properties used to identify them.

Common Gases and the Important Properties used in Identifying them

GasPhysical PropertiesTestResult
Hydrogen, H2(g)Colourless, odourless gas; neutral to litmus paperIgniteBurns with ‘pop’ sound
Oxygen, O2(g)Colourless, odourless gas; neutral to litmus paperInsert a glowing splintThe splint rekindles
Carbon (IV) oxide, CO2(g)Colourless, odourless gas; acidicBubble the gas through lime waterLimewater turns milky
Chlorine, Cl2(g)Greenish-yellow;choking smell(i) Insert moist blue litmus paper

(ii) Insert a moist starch-iodide paper
Litmus paper turns red then becomes bleached to white 
Moist starch-iodide paper turns blue
Ammonia, NH3(g)Colourless;Pungent smell; alkaline(i) Insert moist red litmus paper.(ii) Contact with fumes of concentrated hydrochloric acid.(i) Litmus paper turns blue.
(ii) Gives white dense fume of NH4Cl with HCl.
Hydrogen Chloride, HCl(g)Colourless, odourless;gives acidic solution in water(i) Insert damp blue litmus.
(ii) Apply a drop of silver nitrate on the end of a glass rod and hold it over gas
(i) Litmus paper turns red
(ii) A white precipitate
Hydrogen sulphide, H2S(g)Colorless gas;rotten egg smellTest with damp lead (II) ethanoate (lead acetate) paperLead(II) ethanoate paper turns black
Sulphur (IV) oxide, SO2(g)Colourless, odourless; acidicTest with freshly made potassium dichromate (VI) paperPaper turns from orange to green
Nitrogen (IV) oxide, NO2(g)Reddish brown; pungent smell;Acidic(i). Insert moist blue litmus paper
(ii). Pass into silver trioxonitrate (V) solution
(i). Litmus paper turns red
(ii). Cream precipitate is formed.

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