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Fun Chemistry Question

Discussion in 'Nontraditional Students' started by DrWanahbe, Aug 3, 2006.

  1. DrWanahbe

    DrWanahbe Member
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    Can it be this easy? I have to ID 4 colorless solutions, using only my knowledge from lab. The 4 solution are HCl, ZnCl2, H2S04, and K2SO4.

    Here's what I've got for an answer:

    The first step is to test the pH of each solution, using litmus paper and to compare the results with the color scale, similar to that used in the Reaction Types virtual lab. Based on research of the physical properties, I expect to see 2 of the strips as red (pH about 1), one as yellow (about a pH of 7) and one to be and orange color (about a pH of 4). This will narrow the set down to know which of the two are the acids.

    Next, taking the two acid solutions, I will react each with BaCl2, which was used in the Reaction Types lab. I expect that one will react and form solid white, opaque BaSO4, while the other one will have no reaction. The one that reacts will be identified as H2SO4, sulfuric acid, and the other, with no reaction, HCl, hydrochloric acid.


    This leaves ZnCl2, Zinc Chloride, and K2SO4, Potassium Sulfate. Both can also be combined with BaCl2 as well. Reacting K2SO4 with BaCl2, and will also result in a white opaque precipitate and soluble KCl, while BaCl2 and ZnCl2 will most likely result in no reaction, as both are soluble substances. From this, we will be able to ascertain the identity of the last two solutions.

    Can it really be THIS SIMPLE? I think I'm missing something here...Can anyone with a knack for Gen Chem confirm or deny my thinking???

    Thanks!
     
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  3. Olddodger

    Olddodger Member
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    Sounds like a good plan. Here's a tip from someone who just took 2 semesters of gen chem. Know your solubility tables cold. A lot really revolves around them. When I feel myself getting weak on them, I whip out my note cards.

    Sometimes it's not so cut and dried. There are some compounds that are "kinda sorta" soluble, like barium nitrate, depending on the concentration and the solvent. We use that one in lab to demonstrate LeChat's principle.

    Best,
    Oldie
     
  4. RxnMan

    RxnMan Who, me? A doctor?
    Moderator Emeritus 7+ Year Member

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    As someone who has taught Gen Chem Lab, I think it sounds great. Assuming the BaSO4 will ppt out like you think it will (I don't remember), your plan should work out well.
     

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