How to write chemical equations

  • Thread starter jools111
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  • #1
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Homework Statement



Write and Balance equations for the following reactions:

zinc sulphate + barium nitrate ----->

Homework Equations





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.
 

Answers and Replies

  • #2
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I end up with a mixture of ions initially after mixing them. But there appears to be a compound that is insoluble...
 
  • #3
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I end up with a mixture of ions initially after mixing them. But there appears to be a compound that is insoluble...
So could I use the model for an exchange reaction,

AB + CD ----> AD + CB

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

Does that work?
 
  • #4
Borek
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Does that work?
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).
 
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  • #5
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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...
 
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  • #6
Borek
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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.
 
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  • #7
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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.
 
  • #8
Borek
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Approach it as if you were mixing solutions. So not

ZnSO4 + Ba(NO3)2

but

ZnSO4(aq) + Ba(NO3)2(aq)
 
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  • #9
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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?
 
  • #10
Borek
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most nitrates and sufates are soluble
Most, but not all.
 
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  • #11
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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?
 
  • #12
Borek
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Fourth rule specifically points to what salt will precipitate from the solution.
 
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  • #13
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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....
 
  • #14
Borek
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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.
 
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  • #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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