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Balancing Chemical Equations.

  1. Mar 2, 2009 #1
    1. The problem statement, all variables and given/known data
    1. Li + H2O ->
    2. K + H2O ->
    3. Na + H2O ->
    4. Ca + H2O ->
    5. Mg + H2O ->
    6. Cs + H2O ->
    7. H + At ->
    8. Na + At ->


    2. Relevant equations



    3. The attempt at a solution
    1. 2Li + 2H2O -> H2 + 2LiOH
    2 & 3: Same for 1.

    Others I have no idea how to do. I was NOT taught these and she somehow thinks we were.
     
  2. jcsd
  3. Mar 2, 2009 #2

    mgb_phys

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    Do you have a periodic table?
    Do you know about groups and valence?
    So how many OH each of the metals needs to make a stabel compound.

    ps. In your answer, how many H are on the right side of the equation?
     
  4. Mar 2, 2009 #3
    THe main problem is what the new product is. How would I know what Na + At, would create, etc,
     
  5. Mar 2, 2009 #4

    mgb_phys

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    Lithium is group 1 so it has one outer electron, and so it needs one OH group to plug into.
    Sodium/Potassium are also group one, Magnesium and Calcium are group 2 so have 2 outer electrons and can plug into two OH groups
     
  6. Mar 2, 2009 #5
    I don't really understand. Can you show me examples?
     
  7. Mar 2, 2009 #6
    Four
     
  8. Mar 2, 2009 #7

    mgb_phys

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    Sorry I miscounted - I thought you had made a mistake.
     
  9. Mar 2, 2009 #8

    mgb_phys

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    Do you know why it is 2Li + 2H2O -> H2 + 2LiOH ?

    Lithium has 1 outer electron available for this sort of chemical reaction.
    Oxygen is 2 electrons short.
    Hydrogen is a little odd, it can be thought of as having one extra electron or one short - it has a single electron in an orbit that can hold 2.

    The OH group has 2 spare slots on the oxygen and one of them filled by the hydrogen, so one free slot overall.
    Lithium as we said has one extra electron which fits into this slot, making LiOH.
    Magnesium has 2 outer electrons so needs to attach two OH groups = Mg(OH)2

    Then it's just a matter of counting how many H2O you need to make everything balance.
     
  10. Mar 2, 2009 #9
    So then Mg + 2H2O -> H2 + Mg(OH)2
     
  11. Mar 2, 2009 #10

    mgb_phys

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    Correct.
     
  12. Mar 2, 2009 #11
    Good. What about Hydrogen and Astatine, and sodium and Astatine.

    H + At = ... /kill myself
     
  13. Mar 2, 2009 #12

    mgb_phys

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    Bizarre example, Astatine (if you could get any) is chemically the same as Chlorine - what is the formula for Sodium and Chlorine
     
  14. Mar 2, 2009 #13
    So Na + At -> NaAt

    At + H - > AtH?
     
  15. Mar 2, 2009 #14
    Yer, or HAt is normally the order.
     
  16. Mar 2, 2009 #15

    mgb_phys

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    And you have to balance it so that it's H2 or At2
     
  17. Mar 2, 2009 #16
    Why?
     
  18. Mar 2, 2009 #17

    mgb_phys

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    Because that's how it occurs as as molecules on the left side of the equation
     
  19. Mar 2, 2009 #18
    Does hydrogen travel around in simple atoms? Is it stable in relation to electron valency?

    EDIT:
    It is missing in the original question.

    The Bob
     
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