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O Level Chemistry & IP Chemistry Notes by 10 Year Series Author – Chemistry Specialist

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O Level Chemistry: Qualitative Analysis (QA) Tips

Below is a Table that can help us to identify cations in an unknown solution. This is very important in Qualitative Analysis Tests.

Besides SPA and Practical Examinations where the following table will be provided, you will need to memorize the table in order to answer QA questions that come out for Multiple-Choice Questions as well as Structured Questions.

But no fret, it is not that difficult to memorize it. Start by looking at Cu2+, Fe2+, Fe3+ and NH4+ because they have very distinct colours changes:

  • Cu2+ –> Blue PPT
  • Fe2+ –> Green PPT
  • Fe3+ –> Reddish Brown PPT
  • NH4+ –> Gives Pungent Ammonia Gas upon heating with NaOH
    identifying-cation.jpg (Click Image to have a better view)

PS: Do print a copy and paste it at the end of your notebook if necessary.

Related Articles:

  • O Level Chemistry: Tips on Solubility of Common Salts
  • O Level Chemistry SPA: Color of Copper Hydroxide Vs Copper Carbonate Vs Soluble Copper Salts
  • O Level Chemistry: Tips on Acids, Bases & pH
  • O Level Chemistry: Redox Reaction Question 5
  • O Level Chemistry: Mole Concepts / Qualitative Analysis

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Comments

  1. Sean Chua says

    May 28, 2014 at 12:33 am

    Thanks Sophia for your compliments.

    “Test for Anions” is in fact easier than the “Test for Cations” in my opinion.

    Cos there are only a few Anions they will test you on: Cl-, I-, NO3-, SO42- and CO32-.

    And the test for them are quite distinctive from the other (except that Cl- and I- have similar test and observations”.

    I will suggest that instead of memorising it, perhaps you want to understand the Chemistry of each test. In that way, you will find it easier to remember the tests.

    Enjoy learning Chemistry!

    Sean Chua

  2. Sophia says

    April 29, 2014 at 7:47 pm

    Hello! (: your tips on ‘QA- tests for cations’ really helped me! Do you happen to know any easy ways to remember the tests for anions? That would be a great help! (: thanks for taking the time to read my comment!

  3. sean says

    May 15, 2008 at 1:00 am

    You are right. These hydroxides are amphoteric in nature and will react with
    NaOH to form complexes that are soluble in water.

  4. dona says

    May 14, 2008 at 5:06 am

    ive discovered that when the substances react with NaoH, metal hydroxides r formed.those that are amphoteric react with excess NaoH causing the ppt to dissolve. therefore the ppt is sol. in xs. eg Pb2+, Al3+ & zn2+. correct me if im wrong

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