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Homework Help: Predicting Products

  1. May 30, 2009 #1
    1. The problem statement, all variables and given/known data

    The problem statement is: complete each equation by writing the correct products and identifying the type of reaction.

    2. Relevant equations

    Here are the revelation equations:

    BaO(s) + Mg(s) -->
    CaOH(aq) + HCl (aq) -->
    MgCl(aq) + S(s) -->

    3. The attempt at a solution

    OK. Let me start off by saying that the above equations are not going to be graded by my teacher (I'm in Gr 10 Science). We are given home work, but we have to do it anyway in order to understand it for an evaluation at the end of the week. We also don't correct home work in class and aren't given answers which makes it a little more difficult, so I have read what I could find online, and finally signed up here in order to try to get some clarification on some concepts. If you guys could also help me with some follow up questions along the way, that would be great too.

    First, I figured the first one would be a single displacement resulting in:
    BaO(s) + Mg(s) --> Ba + MgO

    my rationale here is that a switch has to take place where a metal (Mg) pairs up with a non-metal (O). I am assuming it's already balanced.

    Second one seems to be a double displacement which would result in:
    CaOH(aq) + HCl (aq) --> CaCl2 + H2O that would need to be balanced but are the products correct? My understanding is that, once again, a metal to a non-metal.

    Third one seems to also be a single displacement with the products being:
    MgCl(aq) + S(s) -->MgS + Cl

    Are my answers above correct, and if not, could you provide some explanations and tips as to how to correctly predict these products.

  2. jcsd
  3. May 30, 2009 #2


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    Homework Helper
    Education Advisor
    Gold Member

    Your reasoning in the Ba, Mg reaction is unconventional and therefore likely wrong. Can you find reduction potential information to support or reject such a reaction?

    Your Ca reaction makes sense only qualitatively. Your reaction is unbalanced.

    What kind of reaction are you expecting for Mg and S reaction? What is the charge for Mg solid and what is the charge for a Mg ion? What about the possible charges for the use of S (the sulfur and the ion?)?

    If you were more formally studying Chemistry, you would know more clearly how to find answers to some of what you ask. Your teacher should give better instruction about the topic you are currently trying to handle.

    One other comment: Whatever you may think of your current assignment or course, do not let it discourage you about science or Chemistry. Some of this stuff becomes much clearer in courses from community colleges and other colleges and universities. The design of your current assignment seems somewhat incompletely developed.
  4. May 31, 2009 #3


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    Staff Emeritus
    Science Advisor
    Homework Helper

    mico12345, welcome to PF!

    I thought your reasoning made sense in all three cases. However, some of the formulas for reactants appear to be wrong. I'll suggest double-checking the preferred charge states of:


    Hopefully getting the correct formulas will help with balancing the reactions.
  5. May 31, 2009 #4

    I just received an e-mailed from a science teacher online confirming that the answer to this question: "BaO(s) + Mg(s) --> Ba + MgO" was in fact correct.

    I appreciate the words of encouragement, though, because right now I'm at a loss as to how to understand this...

    I've read my text book and articles online explaining synthesis, decomposition, single and double displacement reactions. I understand how to spot them, but when it comes to predicting the products based solely on the reactants alone, I am at a loss as to how to do this. There appears to be nothing in the textbook or online that will explain (step by step) how to go about determining a product based solely on the reactants alone. The only thing I could find is this one tutorial that demonstrates very simple single displacement reactions: http://papapodcasts.blogspot.com/2008/10/single-displacement-reactions-1852.html


    Thanks for the welcome.

    I got the formulas for the reactants directly from the work sheet given, so I just assumed they were correct? :confused:
  6. Jun 1, 2009 #5


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    Staff: Mentor

    Was CaOH there? Or is it CsOH or Ca(OH)2? First is wrong, both latter are OK.
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