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chemistry(balance equation)

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hi!i am a f4 student in hk.i have know the basic concept of balance equation.but some too complex equation i cant there any general short cut for balancing any simple or complex chemical equation?

  • chemistry(balance equation) -

    just look for least common multiples of the atom counts

    For example, if you want to make a hydrogen balloon, a good reaction is lye and aluminum (try it!)

    Al + NaOH = Al(NaO)3 + H2

    The problem is that the right side needs

    Since you're mixing 2's and 3's, you will want to make multiples so that things get used up in 6's

    2Al + 3NaOH = 2Al(NaO)3 + 3H2

    With more complex reactions, things do get more involved, but usually the numbers are relatively small, even with things like burning gasoline (octane):

    2C8H18(g)+25O2(g) = 16CO2(g)+18H2O(g)

  • chemistry(balance equation) -

    so what side should i look for the LCM?

  • chemistry(balance equation) -

    how about HNO3 +Cu ------->Cu(NO3)2+NO+H2O,PLEASE SHOW ME STEPS.

  • chemistry(balance equation) -

    Note that Cu(NO3)2 requires 2 NO3 groups. So, the first step would be to make

    2HNO3 +Cu ------->Cu(NO3)2+NO+H2O

    Now you have the (NO3)2 taken care of.

    On the right we still have NO+H2O = H2NO2, so we need another H2NO3 on the left:

    3HNO3 +Cu ------->Cu(NO3)2+NO+H2O

    Now we are left with an extra O on the left. So, for every 3 NO3 on the left we get 8 O on the right. Sounds like 24 is a good LCM

    8 NO3 + Cu ----> Cu(NO3)2 + NO + 4H2O
    We've used up all the H, but now need to fill in for the NO3 stuff.

    3Cu+ 8HNO3----> 3Cu(NO3)2 + 2NO +4H2O

    That was pretty trial-and-error. Maybe a web search on balancing reaction equations or stoichiometry will yields a more methodical method.

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