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    How are Ammonium Ions identified?
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    Heat the compound, so it decomposes to give off gas. Being the only common alkaline gas, it will turn damp red litmus blue.
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    I thought that if you added sodium hydroxide to it you got ammonia gas given off, then you can test for it with damp litmus paper and it goes blue. I'm sure that's what it says in the specification..
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    (Original post by MadWithStars)
    I thought that if you added sodium hydroxide to it you got ammonia gas given off, then you can test for it with damp litmus paper and it goes blue. I'm sure that's what it says in the specification..
    I thought you heat the ammonia with sodium hydroxide solution.
    Then the gas turns damp red litmus paper blue?

    Correct me if im wrong!
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    the spec just says add NaOH and ammonia is formed.

    For me this is the hardest part of chemistry.

    How do you identify chloride, iodide and bromide ions?
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    Add silver nitrate:
    cream = bromide
    white= chloride
    yellow=iodide
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    (Original post by Hobbesian)
    How do you identify chloride, iodide and bromide ions?
    Add nitric acid to acidify the sample
    Then add a few drops of silver nitrate, and the silver hailde will form:
    AgCl = white
    AgBr = cream
    AgI = yellow
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    Are you all sure it has to be damp litmus paper? We were only told that NH3 gas would turn red litmus blue as it is an alkali..
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    i honostly think it wouldnt matter--

    here is the list of the flame tests we kneed to know

    Litium - red
    Potassium- lilac
    Calcium- brick red
    Sodium - yellow
    Barium - apple green

    How are zinc and copper carbonates detected

    also how are calcium/alluminium/iron 2 and 3/ copper ions detected.
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    (Original post by AliciaK)
    Are you all sure it has to be damp litmus paper? We were only told that NH3 gas would turn red litmus blue as it is an alkali..
    Both work, but it's much easier to waft some damp paper into the gas rather than collect it and bubble it through a solution of litmus.
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    (Original post by Hobbesian)
    i honostly think it wouldnt matter--

    here is the list of the flame tests we kneed to know

    Litium - red
    Potassium- lilac
    Calcium- brick red
    Sodium - yellow
    Barium - apple green

    How are zinc and copper carbonates detected

    also how are calcium/alluminium/iron 2 and 3/ copper ions detected.
    Both carbonates will fizz when a dilute acid is added to them (releasing CO2). But copper will give a blue-green gelatinous precipitate when a few drops of sodium hydroxide solution is added to this. This precipitate will not redissolve. Zinc carbonate will not form such a precipitate.

    Sodium Hydroxide test
    Adding a few drops to these samples confirms these metal ions.
    Calcium: white precipitate which doesn't redissolve when more NaOH is added
    Aluminium: white gelatinous precipitate that will redissolve
    Copper (II): blue-green gel. precip. will not redissolve
    Iron (II): green-grey gel. precip. will not redissolve
    Iron (III): red-brown gel. precip. will not redissolve
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    (Original post by calcium878)
    Both work, but it's much easier to waft some damp paper into the gas rather than collect it and bubble it through a solution of litmus.
    Sorry, I meant we were told that it would turn red litmus paper blue. Not damp red litmus paper.. :confused:
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    (Original post by AliciaK)
    Sorry, I meant we were told that it would turn red litmus paper blue. Not damp red litmus paper.. :confused:
    The gas needs to dissolve first to be able to react with the litmus, hence damp paper is used. I'm not quite sure they would be too picky about this at GCSE level.
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    TBH i think the dampness is to do with allowing it to react with the litmus as i think it has a coating to prevent reaction with air - thats why it is only used with liquids (gases if dampened)
 
 
 

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