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How to write chemical equations

  1. Jun 26, 2010 #1
    1. The problem statement, all variables and given/known data

    Write and Balance equations for the following reactions:

    zinc sulphate + barium nitrate ----->

    2. Relevant equations



    3. The attempt at a solution

    I know that the formulas for the reactants are :

    ZnSO4 + Ba(NO3)2 ---->

    I'm just having a really hard time coming up with the product for these type of questions. I have no problems writing the formulas for the individual compounds, and balancing afterwards is good to go as well. It's the products I'm having trouble with. Can anybody give me a shove in the right direction? Thanks.
     
  2. jcsd
  3. Jun 27, 2010 #2
    I end up with a mixture of ions initially after mixing them. But there appears to be a compound that is insoluble...
     
  4. Jun 27, 2010 #3
    So could I use the model for an exchange reaction,

    AB + CD ----> AD + CB

    ZnSO4 + Ba(NO3)2 ----> Zn(NO3) + BaSO4

    Does that work?
     
  5. Jun 27, 2010 #4

    Borek

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    Staff: Mentor

    In general - no. ZnCl2 + Ba(NO3)2 is no reaction. However, do you know solubility rules? If so, do you see potentially insoluble salt? (That's what Fightfish already signalled).
     
    Last edited by a moderator: Aug 13, 2013
  6. Jun 27, 2010 #5
    I'm not 100% on solubility rules yet... but I'm getting there. I do see that barium sulfate is insoluble. But there are no liquids in this reaction... so how does solubility come into play? Also, you have zinc chloride as the first reactant. Shouldn't it be zinc sulfate? Or have I missed something again...
     
    Last edited: Jun 27, 2010
  7. Jun 27, 2010 #6

    Borek

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    Staff: Mentor

    The only way any reaction may happen is if you mix these salts in solution - when you mix solids, nothing happens. And zinc chloride/barium nitrate was just an example of very similar mixture which doesn't react - it just sits in the solution for ever.
     
    Last edited by a moderator: Aug 13, 2013
  8. Jun 27, 2010 #7
    So the question states:

    Write and balance an equation for the following reaction

    zinc sulphate + barium nitrate

    With both these compunds beings solids.... I understand how there would be no reaction. Am I to assume that a liquid is added, and part of the reaction? I am really confused with this question.
     
  9. Jun 27, 2010 #8

    Borek

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    Staff: Mentor

    Approach it as if you were mixing solutions. So not

    ZnSO4 + Ba(NO3)2

    but

    ZnSO4(aq) + Ba(NO3)2(aq)
     
    Last edited by a moderator: Aug 13, 2013
  10. Jun 27, 2010 #9
    Ok... So based on the general solubility rules, most nitrates and sufates are soluble. Which makes both of our compunds soluble... Can I not apply the exchange rule:

    AB + CD ---> AD + CB

    To give me:

    ZnSO4 + Ba(NO3)2 ---> Zn(NO3)2 + BaSO4

    Even in an aqueous state, the rule should apply right?
     
  11. Jun 27, 2010 #10

    Borek

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    Staff: Mentor

    Most, but not all.
     
    Last edited by a moderator: Aug 13, 2013
  12. Jun 27, 2010 #11
    The rule states:

    2. Most nitrates and acetates are soluble. AgC2H3O2 is moderately soluble.
    4. Most sulfates are soluble except BaSO4, SrSO4, and PbSO4. CaSO4 and Hg2SO4 are moderately soluble.

    If it is not part of the rule, how can I tell what is soluble and what is not?
     
  13. Jun 27, 2010 #12

    Borek

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    Staff: Mentor

    Fourth rule specifically points to what salt will precipitate from the solution.
     
    Last edited by a moderator: Aug 13, 2013
  14. Jun 29, 2010 #13
    I'm sorry... I'm not following. In my book the fourth rule states:

    4. Most sulfates are soluble except BaSO4, SrSO4, and PbSO4. CaSO4 and Hg2SO4 are moderately soluble.

    Would the precipitate not be one of the products? Neither of the reactants in my equation are listed there....
     
  15. Jun 30, 2010 #14

    Borek

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    Staff: Mentor

    Seems like you are missing something... Do you know that salts are dissociated in water? Your solution contains Ba2+, Zn2+, SO42- and NO3-. They can recombine producing 4 possible salts. Of these most are soluble, so they won't precipitate.
     
    Last edited by a moderator: Aug 13, 2013
  16. Jul 17, 2010 #15
    I am a bit confused too... As you have said, the solution contains 4 possible ions that recombine to form 4 possible salts. Since barium sulphate can be formed, why doesn't it precipitate from the reaction?
     
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