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Chemistry ATP (Important points for Both IGCSE and O-level)

Discussion in 'Cambridge O Levels' started by Nibz, May 24, 2011.

  1. WayneRooney10

    WayneRooney10

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    hey!! Can any one give me a list of all the indicators and how they work? Thanks.
     
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  3. TatsuEG

    TatsuEG

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    Oxygen is a poisonous gas , if we inhale it directly from an Oxygen source

    We don't die from oxygen in air , because other gases are in the atmosphere with it


    So I think nitrogen might be a poisonous gas if inhaled directly from the source
    Its just an opinion
    Thanks :)
     
  4. Nibz

    Nibz XPC Global Moderator Staff Member

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    My Bad!
    Sorry.
    That was supposed to be 'Nitrogen Dioxide'!
     
  5. abcde

    abcde

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    Okay! :)
     
  6. burndtjamb

    burndtjamb

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    For which substances can potassium dichromate be used as a test for?
     
  7. TatsuEG

    TatsuEG

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    Universal Indicator:

    Acid ( Red - Yellow) , Neutral ( Green) , Alkaline ( Blue - Violet)


    Phenolphthalein:

    Alkaline ( Pink) For Strong ( Colourless) , Neutral ( Colourless) , Acid ( Orange)

    Methyl Orange:

    Alkaline: ( Yellow) , Neutral ( Colourless) , Acid ( Red)


    P.S Some of the indicators have a trend in colour , such as methyl orange from 1-14 colour becomes more pale

    Hope that helped,
    Thanks
     
  8. TatsuEG

    TatsuEG

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    Testing for Ethanol

    Thanks :)
     
  9. abcde

    abcde

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    To test for the presence of any reducing agent.
     
  10. dancingmaster

    dancingmaster

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    Doesn't phenolphthalein only change colour in alkalis? Isn't it supposed to be colourless in acids? and what about the bromo-something blue? what colour changes does that have? PLEASE HELP!
     
  11. TatsuEG

    TatsuEG

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    It gives colourless on weak acids


    Bromothymol Blue:

    Acid (Yellow) , Neutral (Dark green) , Alkaline (Blue)
     
  12. WayneRooney10

    WayneRooney10

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    Thanks Alot :)
     
  13. babyzee

    babyzee

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  14. babyzee

    babyzee

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  15. TatsuEG

    TatsuEG

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    Here are some Ion testing so you could solve the questions

    http://www.xtremepapers.me/forums/viewtopic.php?f=24&t=667

    All rights reserved to the owner


    Hope it helps :)
     
  16. babyzee

    babyzee

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    Tatueg can you take me through one question like exactly how to do it
     
  17. TatsuEG

    TatsuEG

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    Very well...

    You have been given 3 Aqueous Solutions. K , L , M

    L was identified as sodium hydroxide

    The first question on the table says

    "Ph of L" L is sodium hydroxide which is an alkali

    Alkalis have a range of Ph from 8-14 . Sodium hydroxide is a strong alkali so you should provide any ph from the range of 11-14

    2nd Question in the table says
    What happens if we drop Sodium hydroxide on Copper sulphate

    When Sodium hydroxide is added to Copper ion , a Blue precipitate is formed and does not dissolve in Excess of Sodium Hydroxide

    Only when Excess ammonia is added , It dissolves giving a Pale blue solution as mentioned in the table


    3rd Question in the table says
    If Sodium Hydroxide was added to Aluminium Sulphate
    Results would be

    White precipitate , If in excess would dissolve giving a colourless solution

    K is identified as Aqueous Ammonia

    and M is identified as Hydrochloric acid duo to acidification and adding silver nitrate and forming a white ppt. which is a typical for a chloride ion test , Donot provide only chloride ion for 2 marks provide a chloride compound such as Hydrochloric acid.
     
  18. dancingmaster

    dancingmaster

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    Doesn't phenolphthalein only change colour in alkalis? Isn't it supposed to be colourless in acids? and what about the bromo-something blue? what colour changes does that have? PLEASE HELP![/quote]

    It gives colourless on weak acids


    Bromothymol Blue:

    Acid (Yellow) , Neutral (Dark green) , Alkaline (Blue)[/quote]

    Thanks a lot. Just one more question - Does phenolphthalein change colours in strong acids and if it does, what colour change happens?

    Again thank you so very much.
     
  19. TatsuEG

    TatsuEG

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    Orange colour :)
     
  20. Nibz

    Nibz XPC Global Moderator Staff Member

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    If only I had time!
    You can do that, if possible ! :)
     
  21. Ramosk95

    Ramosk95

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    how would i know when to use the right test for water for example :give a test for pure water in the ms they said boiling then the result is 100 but i wrote copper 2 sulphate and its result!! is that correct???thanks
     

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