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Thread: How Much Oxygen is in Water?

  1. #1 How Much Oxygen is in Water? 
    Time Lord zinjanthropos's Avatar
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    One of the reasons Iím sticking this in here is because Iím hoping someone can explain difference between O & O2 ? Also is O2 a relatively easy bond to break?

    As to thread titleÖ.I used to ask myself this question whenever I heard of a fish dying from lack of oxygenÖ.. I know my mistake was thinking that if water is H2O then it must mean itís 33% oxygen. Youíd think thereís plenty of oxygen to go around. You might also ask yourself what happens to the hydrogen if the oxygen is removed. Anyways I figured thereís something Iím not getting.

    Eventually I got around to thinking that perhaps breathing in water doesnít necessarily mean removing oxygen from the H2O molecule. The only thing I could think of is that there is dissolved oxygen in the water. Having an aquarium and splashing water into it constantly kind of told me thatís the secret. Probably not 100% correct but has to have something to do with it. I was just checking oxygen in water on Google when I was reminded of it.

    https://www.waterontheweb.org/under/...cent%20oxygen.


    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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  3. #2  
    KJW
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    Quote Originally Posted by zinjanthropos View Post
    The only thing I could think of is that there is dissolved oxygen in the water.
    This.

    The only way to extract elemental oxygen (O2) from water is some form of oxidation, such as occurs in photosynthesis. In the case of photosynthesis, one has the half-reaction:

    2 H2O —> O2 + 4 H+ + 4 e

    The electrons ultimately (by a complicated set of reactions) reduce carbon dioxide.


    There are no paradoxes in relativity, just people's misunderstandings of it.
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    Quote Originally Posted by KJW View Post

    The only way to extract elemental oxygen (O2) from water is some form of oxidation, such as occurs in photosynthesis. In the case of photosynthesis, one has the half-reaction:

    2 H2O —> O2 + 4 H+ + 4 e

    The electrons ultimately (by a complicated set of reactions) reduce carbon dioxide.
    And the reactions which produce molecular oxygen (O2) are conducted by a complex of proteins which arose a very long time again, and eventually oxygenated Earth's atmosphere, dramatically changing the course of evolution. This membrane bound structure is known as the "photosynthetic reaction center"*.

    The evolution of this mechanism must have been rather involved, since it is much more complex to derive biological energy from light than it is from other chemicals. Life arose by strictly chemical processes, with photosynthesis arising from the earliest microbial forms.


    * https://en.wikipedia.org/wiki/Photos...eaction_centre
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    Quote Originally Posted by zinjanthropos View Post
    One of the reasons I’m sticking this in here is because I’m hoping someone can explain difference between O & O2 ? Also is O2 a relatively easy bond to break?
    Forgot to answer your primary question on oxygen forms. For Earth, monoatomic oxygen (O) exists in the upper atmosphere where it is broken down from O2 by UV. It is extremely reactive and does not persist at ground level.

    Molecular oxygen (O2) exists throughout the atmosphere, but it too is highly reactive and requires photosynthesis to maintain its presence. So its bonds are rather easy to break. As such, it is highly reactive, and it attacks many substances. Metals are a common target, with which it forms oxides, rust being a common example.

    And then there is another molecular form : O3, ozone, which also forms in the atmosphere by UV, and is also very reactive. It is also a component of air pollution from exhaust emissions and the primary part of smog. Also highly reactive.

    It can get rather involved, but the chemistry of these various forms of elemental oxygen have unique properties. If you are up for a long read, try :


    https://en.wikipedia.org/wiki/Oxygen
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    Quote Originally Posted by zinjanthropos View Post
    One of the reasons I’m sticking this in here is because I’m hoping someone can explain difference between O & O2 ? Also is O2 a relatively easy bond to break?

    As to thread title….I used to ask myself this question whenever I heard of a fish dying from lack of oxygen….. I know my mistake was thinking that if water is H2O then it must mean it’s 33% oxygen. You’d think there’s plenty of oxygen to go around. You might also ask yourself what happens to the hydrogen if the oxygen is removed. Anyways I figured there’s something I’m not getting.

    Eventually I got around to thinking that perhaps breathing in water doesn’t necessarily mean removing oxygen from the H2O molecule. The only thing I could think of is that there is dissolved oxygen in the water. Having an aquarium and splashing water into it constantly kind of told me that’s the secret. Probably not 100% correct but has to have something to do with it. I was just checking oxygen in water on Google when I was reminded of it.

    https://www.waterontheweb.org/under/...cent%20oxygen.
    Yes, it is O2 dissolved in water.

    With gases, the amount a polar solvent can dissolve declines as the temperature rises, i.e. the opposite of what generally happens when dissolving solids. This is one reason why, when water becomes too warm, the fish can start to suffocate and you may see them come to the surface and even gulp air. Having water pass over a weir or bubbling air into it can help. On the Thames in summer there is a vessel called the Thames Bubbler, whose job it is to aerate the water at points where the oxygen levels fall too low, in order to keep the fish alive and able to move up and down the river. This decline of solubility of air with temperature also accounts for the annoying noise of air in my central heating system, which has just had a new boiler ("furnace" in American-speak). When it reaches max temperature air starts to come out of solution and accumulates at certain points. I am told that after a while the water in the heating circuits will have degassed enough for this to stop.
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  7. #6  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by zinjanthropos View Post
    One of the reasons I’m sticking this in here is because I’m hoping someone can explain difference between O & O2 ? Also is O2 a relatively easy bond to break?

    As to thread title….I used to ask myself this question whenever I heard of a fish dying from lack of oxygen….. I know my mistake was thinking that if water is H2O then it must mean it’s 33% oxygen. You’d think there’s plenty of oxygen to go around. You might also ask yourself what happens to the hydrogen if the oxygen is removed. Anyways I figured there’s something I’m not getting.

    Eventually I got around to thinking that perhaps breathing in water doesn’t necessarily mean removing oxygen from the H2O molecule. The only thing I could think of is that there is dissolved oxygen in the water. Having an aquarium and splashing water into it constantly kind of told me that’s the secret. Probably not 100% correct but has to have something to do with it. I was just checking oxygen in water on Google when I was reminded of it.

    https://www.waterontheweb.org/under/...cent%20oxygen.
    Yes, it is O2 dissolved in water.

    With gases, the amount a polar solvent can dissolve declines as the temperature rises, i.e. the opposite of what generally happens when dissolving solids. This is one reason why, when water becomes too warm, the fish can start to suffocate and you may see them come to the surface and even gulp air. Having water pass over a weir or bubbling air into it can help. On the Thames in summer there is a vessel called the Thames Bubbler, whose job it is to aerate the water at points where the oxygen levels fall too low, in order to keep the fish alive and able to move up and down the river. This decline of solubility of air with temperature also accounts for the annoying noise of air in my central heating system, which has just had a new boiler ("furnace" in American-speak). When it reaches max temperature air starts to come out of solution and accumulates at certain points. I am told that after a while the water in the heating circuits will have degassed enough for this to stop.
    Thats what I thought....fish gills remove dissolved oxygen. No wonder the fish in the Niagara River below the cataract look pretty healthy....still wouldn't eat one. People do however. When I was younger the Americans had a chemical plant above the falls but long since gone. No local sushi dining for me.

    Have you tried bleeding your house radiators? Should be a little valve you can open on each. Open & wait until water flows thru then close it. Some lines are equipped with automatic bleed valve installed near or above boiler. If old it may be blocked. Looks like a small (4" high approx) little brass silo.
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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