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Thread: why is CO2 an acidic gas?

  1. #1 why is CO2 an acidic gas? 
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    Simply put (please correct if I am being too base [excuse the pun!]) - an acid has excess hydrogen ion activity whereas an alkaline is one that has excess oxygen activity (or should I even say potential?).......

    CO2 has oxygen and no hydrogen, so why is it an acidic gas?

    Wiki says that it is considered so as CO2 reacts with water to 'excite' the hydrogen ions, is there an explination to this?

    thanks.........


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  3. #2  
    Reptile Dysfunction drowsy turtle's Avatar
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    Carbon dioxide reacts with water to produce carbonic acid:



    Carbonic acid is an acid because one or both of the hydrogen atoms can dissociate and become H+ ions.


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  4. #3  
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    ah........so are the hydrogen bonds weak in comparison to the oxygen ones making it more of an acid then an alkaline?
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    Quote Originally Posted by fatman57
    ah........so are the hydrogen bonds weak in comparison to the oxygen ones making it more of an acid then an alkaline?
    I'm not sure exactly what you mean by that.

    An acid is any compound that can release H+ ions in solution.

    An alkali is any compound that can remove H+ ions from solution.

    (In different situations, a single compound can either accept or donate an H+ ion)

    Carbonic acid acts as an acid, because the hydrogen atoms can leave the molecule as cations, and move freely in the solution.

    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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    ok, that makes sense.

    please excuse me i'm learning..........it all makes sense now.........

    out of interest is carbonated water an acid?
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    Reptile Dysfunction drowsy turtle's Avatar
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    Quote Originally Posted by fatman57
    please excuse me i'm learning..........
    No problem, we're all learning.

    Quote Originally Posted by fatman57
    out of interest is carbonated water an acid?
    Yup. It's the acid that makes it taste fizzy (not the bubbles).
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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    thanks..............I presume the bubbles are CO2 gas that hasn't reacted with the water....................like they add more gas then would react with the volume of water they are using so it remains as a gas and 'fizzes'.........????
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  9. #8  
    Forum Professor Wild Cobra's Avatar
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    Quote Originally Posted by drowsy turtle
    Quote Originally Posted by fatman57
    please excuse me i'm learning..........
    No problem, we're all learning.

    Quote Originally Posted by fatman57
    out of interest is carbonated water an acid?
    Yup. It's the acid that makes it taste fizzy (not the bubbles).
    No kidding. I really feel sorry for those who think they have nothing to learn in life.
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  10. #9  
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    Quote Originally Posted by Wild Cobra
    Quote Originally Posted by drowsy turtle
    Quote Originally Posted by fatman57
    please excuse me i'm learning..........
    No problem, we're all learning.

    Quote Originally Posted by fatman57
    out of interest is carbonated water an acid?
    Yup. It's the acid that makes it taste fizzy (not the bubbles).
    No kidding. I really feel sorry for those who think they have nothing to learn in life.
    kidding..............i feel sorry for those that do!!!
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  11. #10  
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    Quote Originally Posted by fatman57
    thanks..............I presume the bubbles are CO2 gas that hasn't reacted with the water....................like they add more gas then would react with the volume of water they are using so it remains as a gas and 'fizzes'.........????
    Something like that. dissolving in water is a reversible reaction, as is the reaction that converts it into carbonic acid. In a sealed bottle, carbon dioxide bubbles are constantly leaving the solution and rising to the top, and then dissolving all over again because of the pressure in the bottle forcing it into solution. When you leave a glass of fizzy water, it goes flat because mroe of the carbon dioxide leaves the water than dissolves into it from the atmosphere, because there's a very low concentration of carbon dioxide in the atmosphere; not enough to replace what leaves the solution (or not as fast).

    It will reach an equilibrium, where is entering and leaving solution at the same rate, and the concentration of dissolved will remain pretty much the same from that point onwards. So, in theory, leave a glass of fizzy water open to the atmosphere for a suitable length of time, and it should turn into (effectively: there might be other dissolved substances in it that I'm not aware of) normal drinking water.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  12. #11  
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    Quote Originally Posted by drowsy turtle
    Quote Originally Posted by fatman57
    thanks..............I presume the bubbles are CO2 gas that hasn't reacted with the water....................like they add more gas then would react with the volume of water they are using so it remains as a gas and 'fizzes'.........????
    Something like that. dissolving in water is a reversible reaction, as is the reaction that converts it into carbonic acid. In a sealed bottle, carbon dioxide bubbles are constantly leaving the solution and rising to the top, and then dissolving all over again because of the pressure in the bottle forcing it into solution. When you leave a glass of fizzy water, it goes flat because mroe of the carbon dioxide leaves the water than dissolves into it from the atmosphere, because there's a very low concentration of carbon dioxide in the atmosphere; not enough to replace what leaves the solution (or not as fast).

    It will reach an equilibrium, where is entering and leaving solution at the same rate, and the concentration of dissolved will remain pretty much the same from that point onwards. So, in theory, leave a glass of fizzy water open to the atmosphere for a suitable length of time, and it should turn into (effectively: there might be other dissolved substances in it that I'm not aware of) normal drinking water.
    wow thanks, thats very enlightening!!!
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  13. #12  
    Reptile Dysfunction drowsy turtle's Avatar
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    It's all based around le Chatelier's Principle, just in case you're wondering/never heard of it.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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