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A simple experiment to determine an unknown powder

  1. Apr 8, 2013 #1
    1. The problem statement, all variables and given/known data
    You are given a white powder and it could be one of six substances: calcium carbonate, calcium sulfate, sodium hydrogen carbonate, sodium carbonate, sodium chloride and sodium hydroxide. Determine the unknown sample.
    Materials: White powder (5g)
    Phenolphthalein
    Silver nitrate solution
    Acetic acid

    3. The attempt at a solution
    React with acetic acid if it is a carbonate it will bubble (CO2 formed)

    React with the silver nitrate solution if it is sodium chloride it will form a cloudy white solution:
    AgNO3 + NaCl → AgCl(s) + NaNo3

    Now the phenolphthalein changes from colourless to pink when the pH goes above 8.2 so I assume there is some way to find out which one using basic acidic but this is where I start to have trouble as I am unsure what other experiments to do.
    Thanks for the help
     
  2. jcsd
  3. Apr 8, 2013 #2

    chemisttree

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    Gold Member

    What is the solubility of silver carbonate? Silver sulfate?
     
  4. Apr 10, 2013 #3

    AGNuke

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    Gold Member

    I'd like to first use phenolphthalein to check whether the given salt is basic or not. It will really classify them in broad sense.

    Check how many are basic enough to give positive tests with phenolphthalein?
     
  5. Apr 19, 2013 #4

    NascentOxygen

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    Staff: Mentor

    If you continue to add powder to a sample of acetic acid after bubbling ceases, you will be able to see whether that powder is soluble (i.e., forms an aqueous solution).

    You aren't provided with water to test the powders for solubility, so use some spent acid as your water source.
     
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