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  1. #1 chemical equation 
    icu
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    Hey, i am new here, how do u get the product in a chemical equation?
    like 2Mg + O2 --> 2MgO

    can anyone explain how u get the 2MgO?
    and i hv tryed to search for the answer in sites

    thanks in advance


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  3. #2  
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    You have to have the same number of each element on both sides of the equation.


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  4. #3  
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    do you mean how you get MgO

    or how you get the amount of it like balancing the numbers?

    in the first question. because thats how it reacts put simply.
    magnesium + oxygen goes to MgO

    in the second question. you have to look at number of atoms on each side of the equation and balance it.
    you cant change small numbers like the 2 in O2.
    but you can add any number to the front of a molecule to make it balance
    everything is mathematical.
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  5. #4  
    icu
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    i already know how to balance it, for instance:

    C2H6 + O2 --> ?

    like this for example, how do u get the product?

    and thanks heaps for yr help :-D
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    It depends on what's reacting. C2H6 (ethane) is a hydrocarbon and you are combusting it (you know this from the O2). Therefore the products are going to be CO2 and H2O.

    2C2H6 + 7O2 --> 4CO2 + 6H2O
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  7. #6  
    icu
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    how do u know that u get H2O and CO2?
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    If you had fewer than 7 moles of oxygen per 2 moles of ethane you would produce some CO as well as or instead of CO2, partial oxidation being a widespread industrial process. At some dilution (too much ethane or too much oxygen) the reaction wouldn't even start. So your question is a good one and the simple answer is we know from experience what will happen. I suspect you're looking for a more fundamental answer though, which I can't provide.
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  9. #8  
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    Quote Originally Posted by icu
    how do u know that u get H2O and CO2?
    because it is a combustion. you need to recognise reactants and the sorts of reactions they predict; you can't get it all if you just think of them as letters and numbers. Salts dissolve, acids and bases dissociate, that sort of thing.

    based on rancidchickens answer above, can you work out what happens when you metabolise glucose?

    C6H12O6 + O2 -->

    (you'll need to balance both sides)
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  10. #9  
    icu
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    ok, correct me if i am wrong

    but is it C6H12O6 + 6O2 --> 6CO2 + 6H2O

    like acid + oxygen --> carbon dioxide + water
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  11. #10  
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    Quote Originally Posted by icu
    ok, correct me if i am wrong

    but is it C6H12O6 + 6O2 --> 6CO2 + 6H2O

    like acid + oxygen --> carbon dioxide + water
    The equation is right, but glucose is not an acid, it's a carbohydrate ... (carbohydrate=hydrated carbon, see?)

    Good job on balancing the equation though!
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  12. #11  
    icu
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    ty free radical, but what makes a carbohydrate=hydrated carbon?

    for example acid is an acid because it has hydrogen ions in them, and bases have hydroixde ion in them so what about carohydrate?

    thanks in advance :-D
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    acid is an acid because it has hydrogen ions in them, and bases have hydroixde ion in them
    not strictly correct.

    there are many different definitions for acid and bases.
    i think what you're talking about is a bronsted-lowry acid/base

    in this case an acid is a proton (H+) donator
    whereas a base is a proton (H+) acceptor.

    this explains why ammonia (NH3) is a base. it accepts H+ to form the
    NH4+ ion
    everything is mathematical.
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  14. #13  
    icu
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    [quote="organic god"]
    acid is an acid because it has hydrogen ions in them, and bases have hydroixde ion in them
    not strictly correct.

    so this is wrong, the teacher taught me this? and what makes a carbohydrate=hydrated carbon?

    thanks
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  15. #14  
    Forum Masters Degree organic god's Avatar
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    you're teacher probably taught you a simplified version.

    the correct version is acid is H+ donator, base is H+ acceptor,
    ask your teacher
    everything is mathematical.
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  16. #15  
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    [quote="icu"]
    Quote Originally Posted by organic god
    acid is an acid because it has hydrogen ions in them, and bases have hydroixde ion in them
    not strictly correct.

    so this is wrong, the teacher taught me this? and what makes a carbohydrate=hydrated carbon?

    thanks
    It's sort of a mnemonic to help you. A carbohydrate is, technically, more or less defined as having a stoichiometry of C:H:O of 1:2:1.

    Water (this is your hydration) has a stoichiometry of H:O of 2:1 (H2O). So, if a carbohydrate is (CH2O)n then it is a hydrated (H2O) carbon (C).

    CH2O = carbo-hydrate.

    Carbohydrates are burned by you when you exercise, to make energy. You need oxygen to burn things, including carbohydrates.

    Sugar is C6H12O6, or (CH2O)6, but there are other carbohydrates as well, loads of them. And any of them combined with oxygen will give you CO2 and H2O, and you just have to balance the equations.

    Hydrocarbons (ethane, like in your second post) also burn in the presence of oxygen. This is why rancidchicken said that the O2 is an indication of a combustion (burning).... and so now you might recognise these sorts of reactions more easily?

    Acids and bases are different, buffers are different, etc etc - you'll probably be busy learning different types of reactions for a while but it sounds like you are picking it up which is great.




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  17. #16  
    icu
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    hey thanks, and can anyone explain why here has a bracket?

    Mg2 + OH- ---> Mg(OH)s

    thanks :-D
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  18. #17  
    Forum Masters Degree organic god's Avatar
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    you sure you got that equation right?


    the bracket is there to show there is 2 lots of (OH), not 2 hydrogens
    everything is mathematical.
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  19. #18  
    icu
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    ya, but why does here have bracket?

    Fe3 + OH- ---> Fe(OH)3

    and here doesn't here have bracket?

    Cu + CO23 ---> Cu2CO3


    thanks
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    Fe3 + OH- ---> Fe(OH)3
    Btw this should be:
    Fe + 3OH- ---> Fe(OH)3

    The brackets mean you have three -OH's. OH is a polyatomic ion.

    Cu + CO23 ---> Cu2CO3
    I don't know what you're trying to do here. It's not balanced right.

    You should just grab a chemistry text book and take a look at it. You'll probablly understand this much better than someone can explain to you on a forum.
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  21. #20  
    icu
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    but isn't iron is Fe3+?


    thanks :-D
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  22. #21  
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    Yes. Iron is Fe3+ (in that case), so you need 3 OH-'s to get a 0 charge.
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  23. #22  
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    I think you might be confused about valence which is usually indicated as a superscript, and the number of ions in a molecule which is usually indicated by a subscript. I don't think we can show sub and superscripts on here (?).

    Magnesium hydroxide is Mg(OH)2. The bracket means you need 2 OH- ions for one Mg++ ion to make a stable molecule. Magnesium has a +2 valence. The hydroxide ion has a -1 valence. The pluses and minuses have to balance. As organic god wrote, the bracket followed by the 2 is to show there are two OH- ions in the molecule.

    Ferric iron has a +3 valence so you need three OH- ions to balance, hence Fe(OH)3.

    Copper has a +2 valence and the carbonate ion has a -2 valence, so you only need one of each to balance and you don't need brackets because you don't have to indicate multiple carbonate ions. The correct formula is CuCO3.
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  24. #23  
    icu
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    how about this?

    H + CO23?

    thanks
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  25. #24  
    icu
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    Quote Originally Posted by icu
    how about this?

    H + CO23 ---> H2CO3?

    this dont equal a 0 charge?

    thanks
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  26. #25  
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by Bunbury
    I think you might be confused about valence which is usually indicated as a superscript, and the number of ions in a molecule which is usually indicated by a subscript. I don't think we can show sub and superscripts on here (?).

    Magnesium hydroxide is Mg(OH)2. The bracket means you need 2 OH- ions for one Mg++ ion to make a stable molecule. Magnesium has a +2 valence. The hydroxide ion has a -1 valence. The pluses and minuses have to balance. As organic god wrote, the bracket followed by the 2 is to show there are two OH- ions in the molecule.

    Ferric iron has a +3 valence so you need three OH- ions to balance, hence Fe(OH)3.

    Copper has a +2 valence and the carbonate ion has a -2 valence, so you only need one of each to balance and you don't need brackets because you don't have to indicate multiple carbonate ions. The correct formula is CuCO3.
    Mg<sup>+2</sup> + 2OH<sup>-1</sup> = Mg(OH)<sub>2</sub> ?

    Just use the < instead of the [ and it works with "sup" and "/sup" and so on.
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  27. #26  
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    just use the < instead of the [ and it works with "sup" and "/sup" and so on.
    Thanks sunshine, I did not know that.


    how about this?

    H + CO23?
    How about this: H<sup>+</sup> + CO<sub>3</sub><sup>2-</sup>

    How many hydrogens do you need to get zero charge?
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  28. #27  
    icu
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    two?

    thanks
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  29. #28  
    icu
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    i think i got it
    you will need 2 hydrogen to get a zero charge therefore the equation is

    H2+ + CO3- ---> H2CO3

    correct me if i am wrong


    Thanks
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  30. #29  
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    Right, you need two hydrogens. But the equation isn't balanced until you have the two hydrogens on the left side.

    2H<sup>+</sup> + CO<sub>3</sub><sup>2-</sup> ---> H<sub>2</sub>CO<sub>3</sub>
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  31. #30  
    icu
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    cool,can u tell me why it cant be on the right side? because isn't hydrogen a diatomic atom H2?or does it only apply to superscript not subscript?

    thanks
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  32. #31  
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    If you put the 2 on the right hand side of the H as in H<sub>2</sub> you are describing a molecule of hydrogen, which is diatomic, and is electrically neutral. It is not then an ion, it is two atoms bonded together.
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  33. #32  
    icu
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    ok, thanks bunbury, do u have any examples that has a bracket in it, i want to see if i have got it or not :-D

    thanks
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  34. #33  
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    Look up ammonium sulfate (sulphate).
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  35. #34  
    icu
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    NH4 + SO24 ---> NH4(SO24)

    is it right?

    thanks :-D
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  36. #35  
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    NH4 has a positive charge (NH4+). And what do you mean by SO24? 4SO2?
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  37. #36  
    icu
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    i dont know, i am trying to work out the chemial equation for ammonium sulfate (sulphate).

    one day my teacher were talking about predicting charges eg. Na= 2,8,1 = Na+, P = 2,8,5 = P-3 etc....
    and then she said that Si= 2,8,4 can equal Si-4 or Si+4, and i think she said it depends on the bond, can anyone tell me which one is right and more about this...

    much appercaited, thanks :-D
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  38. #37  
    icu
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    correct me if i am wrong....

    2Na + O2 ---> Na2O

    so what i am doing here is that to balance the superscript of O and the subscript of Na? correct? so we put two on the left hand side of Na?

    Al + 3Cl ---> AlCl3

    so over here do we balance the superscript of Al and the subscript of Cl?

    thanks
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  39. #38  
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    2Na + O2 ---> Na2O

    so what i am doing here is that to balance the superscript of O and the subscript of Na? correct? so we put two on the left hand side of Na?
    Perhaps the notation convention has changed in the 40 years since I did this, but it's a little confusing to write about superscripts and subscripts when you put everything on the same line. I think if you mean this you are correct:

    2Na<sup>+</sup> + O<sup>2-</sup> = Na<sub>2</sub>O

    Try to use the code that sunshinewarrior explained so we can all talk the same language.
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  40. #39  
    icu
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    ok, i use to know how to do it but i forgot
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  41. #40  
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    Quote Originally Posted by icu
    ok, i use to know how to do it but i forgot
    It's easy. As I said earlier:

    Mg+2 + 2OH-1 = Mg(OH)2 ?

    Just use the < instead of the [ and it works with "sup" and "/sup" and so on.
    If this seems too elliptical, most coding we use here uses the square brackets [ and ]. If, however, you use the chevrons (for want of a better word) < and > to start and end a code, "sup" for superscript and "sub" for subscript, then you should find it quite easy.
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  42. #41  
    icu
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    like this?
    Cu<2
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  43. #42  
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    No, like this

    Code:
    Cu<sup>2+</sup>
    and

    Code:
    SO<sub>4</sub><sup>2-</sup>
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  44. #43  
    icu
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    ok thanks heaps guys :-D

    one day my teacher were talking about predicting charges eg. Na= 2,8,1 = Na<sup>+</sup>, P = 2,8,5 = P<sup>-3</sup> etc....
    and then she said that Si= 2,8,4 can equal Si<sup>-4</sup> or Si<sup>+4</sup>, and i think she said it depends on the bond, can anyone tell me which one is right and more about this...

    much appercaited, thanks
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  45. #44  
    icu
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    hi

    correct me if i am wrong....

    Na<sup>+</sup> + O<sup>2-</sup> ---> Na<sub>2</sub>O

    so what i am doing here is that to balance the superscript of O with the subscript of Na? correct? so we put two on the left hand side of Na?

    Al<sup>3+</sup> + Cl<sup>-</sup> ---> AlCl<sup>3</sup>

    so over here do we balance the superscript of Al with the subscript of Cl?

    thanks
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  46. #45  
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by icu
    ok thanks heaps guys :-D

    one day my teacher were talking about predicting charges eg. Na= 2,8,1 = Na<sup>+</sup>, P = 2,8,5 = P<sup>-3</sup> etc....
    and then she said that Si= 2,8,4 can equal Si<sup>-4</sup> or Si<sup>+4</sup>, and i think she said it depends on the bond, can anyone tell me which one is right and more about this...

    much appercaited, thanks
    Silicon, carbon etc, have half-filled shells of 8, which means they can be considered to be either having 4 extra, or 4 fewer electrons than are necessary to fill their shells. As a result of this, they have special properties (including organic chemistry, silicons affinity for 'doping' and so on). Whether they behave as +4 or -4 will therefore depend upon circumstance.

    Steve F or other better chemists can correct any serious errors of mine.
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  47. #46  
    icu
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    cool, np thanks for your help anyway
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  48. #47  
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by icu
    hi

    correct me if i am wrong....

    Na<sup>+</sup> + O<sup>2-</sup> ---> Na<sub>2</sub>O

    so what i am doing here is that to balance the superscript of O with the subscript of Na? correct? so we put two on the left hand side of Na?

    Al<sup>3+</sup> + Cl<sup>-</sup> ---> AlCl<sup>3</sup>

    so over here do we balance the superscript of Al with the subscript of Cl?

    thanks
    Ideally you'd write the first equation as:

    2Na<sup>+</sup> + O<sup>2-</sup> = Na<sub>2</sub>O

    The valences on the left side need to cancel each other out, and the number of atoms on the left and right sides need to balance each other out. In fact, you'd be encouraged to write it (if it didn't become so cumbersome) as:

    4Na<sup>+</sup> + O<sub>2</sub><sup>2-</sup> = 2Na<sub>2</sub>O

    This is because we tend to use molecular oxygen (O<sub>2</sub>), rather than single atoms (O), in chemical reactions and this way makes the equation more realistic.

    Using this convention, your second equation is probably best written as:

    Al<sup>3+</sup> + 3Cl<sup>-</sup> = AlCl<sub>3</sub>

    Does this help?


    Edit: Ooops. Edited for typo.
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  49. #48  
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    ‘ang on a minute.

    Please correct me if I’m wrong (it’s been about a million years since I did this in school), but the oxygen molecule has all its shells filled by virtue of the covalent bond between the two oxygen atoms, so it’s not correct to show an oxygen molecule with a valency. The molecule has no charge. You’d write the reaction equation without the valencies thus:

    4Na + O<sub>2</sub> = 2Na<sub>2</sub>O

    innit?
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  50. #49  
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by Bunbury
    ‘ang on a minute.

    Please correct me if I’m wrong (it’s been about a million years since I did this in school), but the oxygen molecule has all its shells filled by virtue of the covalent bond between the two oxygen atoms, so it’s not correct to show an oxygen molecule with a valency. The molecule has no charge. You’d write the reaction equation without the valencies thus:

    4Na + O<sub>2</sub> = 2Na<sub>2</sub>O

    innit?
    You're right, of course. I was waiting for one of you knowledgeable buggers to show I'd been gassing. But what about the Sodium valence then?

    Ah heck... icu can have fun figuring it out, eh?
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  51. #50  
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    whats a mole?
    Time is a great teacher, but unfortunately it kills all its pupils ... - Louis Hector Berlioz
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  52. #51  
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    Mole is a unit for particles.
    If you have a mole of particles it means that you have Avogadros number of the particles, i.e. approximately 6*10<sup>23</sup>
    373 13231-mbm-13231 373
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  53. #52  
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    Mole : is the molecular or atomic weight expressed in grams
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