Dissolved Oxygen Do Or Dissolved O2: Fill & Download for Free

There is slight misconception of the chemistry of water evident in your question.Water is formed from hydrogen gas (H2) and oxygen gas (O2) by combustion. The formula for this reaction is 2H2 + O2 -> 2H2O. This reaction can be reversed by a process called electrolysis. Electricity provides the energy. Fish do not do this.Water is an interesting substance. Atmospheric gases such as oxygen, nitrogen and carbon dioxide go into solution in water. Pop is a super saturated solution of sugar water and carbon dioxide.Fish extract the dissolved oxygen out of the water. If there is no dissolved oxygen in the water the fish will suffocate. Oceanic dead zones are places where dissolved oxygen has been depleted by decaying vegetation.

By mass, table salt is 61% chlorine.Breathing in a gaseous mixture with as little as 1,000 ppm chlorine gas (0.1%) will kill you in minutes.How come consuming table salt doesn’t kill you instantly?Because a compound comprised partly of a given element is not the same as that element in its pure form.Simply having oxygen atoms in our lungs isn’t enough to breathe. We need specifically O2—molecular, gaseous oxygen.If any other form of oxygen is present, it can be useless or worse than useless.For instance, CO2 is carbon dioxide—a mildly toxic gas that we produce as a byproduct of our oxygen consumption, and which we exhale with every breath. But if we try to breathe CO2 (without adequate O2 available), we’ll suffocate.CO is carbon monoxide—a considerably more toxic gas that actually displaces O2 in our bloodstream, again causing asphyxiation.N2O is nitrous oxide—”laughing gas”. It’s a common general anaesthetic, and will make you loopy, but in high quantities, that’ll kill you too.H2SO4 is sulfuric acid… do not try breathing that (even or especially in gaseous form), unless you like your lungs melting. (Insert obligatory “Johnny was a chemist…”)Even O (a single, unbound oxygen atom) is called a “free radical” and is actually incredibly destructive to cells. It’s what we’re trying to get rid of when we eat or drink “antioxidants” for health.Water is H2O.The oxygen that comprises ~89% of the mass of a water molecule is bound to those two hydrogen molecules, so it’s useless to our respiratory process.To “breathe water” we’d have to have some metabolic mechanism that would:Break down water into 2 H+ and 1 O-.Bind 2 O- together into O2 rapidly and efficiently to avoid free radical damage.Alkalize the bloodstream (or pulmonary mucus, or wherever) to counter the pH drop brought on by those H+’s floating around.First off, that would take up a lot of energy—probably more energy than the respiration of the resulting O2 would produce (because, remember, respiration is really, at its core, an energy production process).Second, that process of re-alkalizing the blood would require an ion of the form… OH-. In other words, you’d need to replace as many oxygen atoms as you’d gain, making it an utterly pointless process.Now, that being said, some species do “breathe water” even though they need the same O2 we need.What gives?They’re not literally “breathing water”. They’re filtering dissolved oxygen out of the water.That is, most water has O2 sort of “floating around” in it, like the CO2 bubbles in a can of soda, so fish gills (and other various “water-breathing” physiological structures) are just taking that O2 out of the water, like sifting gold out of sand—it doesn’t mean the sand itself is part gold.If humans could “breathe water” someday, that’s how it would work—we’d be breathing O2 that is simply suspended in surrounding H2O. Although, since we need a lot more O2 than a fish, it would need to be water that has been supersaturated with oxygen.Original Question:“By mass, water is 88.81% oxygen. Air is only 21% oxygen. How come we can't breathe water?”

Hey Vijaya , I think you have a little confusion. Fresh water contains more DO than sea water. Here is why!!!Dissolved oxygen (DO) is the amount of oxygen (O2) dissolved in the water. Dissolved oxygen is one of the best indicators of water quality. People need oxygen in the atmosphere to survive and animals that live in the ocean, like fish, need dissolved oxygen in the water to survive.The amount of dissolved oxygen that the water can hold depends on the temperature and salinity of the water. Cold water can hold more dissolved oxygen than warm water and fresh water can hold more dissolved oxygen than salt water. So the warmer and saltier the water, the less dissolved oxygen there can be. The maximum amount of dissolved oxygen that the water can hold is called the saturation value. Dissolved oxygen measurements are given as a percent of saturation (%) or in units of milligrams per liter (mg/l).Oxygen enters the water at the surface of the water where exchange between the atmosphere and the water can take place. Waves and wind help put oxygen into the water. Dissolved oxygen is also put into the water as a byproduct of phytoplankton photosynthesis. The oxygen found in the deeper water comes from mixing with surface water. Photosynthesis can cause the water to have more dissolved oxygen than the saturation amount. When that happens it is called supersaturation.Animals, such as fish, breathing in the water consume dissolved oxygen. It is also used in the break down of organic matter. As organic matter sinks to the sea floor it begins to decompose. Bacteria in the water use oxygen to break down this organic material. When there is a lot of organic debris, the dissolved oxygen in the deeper water can be used up. If the water at the surface (which has plenty of dissolved oxygen) is not mixed with the deeper water layers form and the water becomes stratified. Then there is no new dissolved oxygen for the deep water. When this happens, the deep water can become unhealthy.Above 5 mg/l dissolved O2, most marine plants and animals have plenty of oxygen. When the dissolved oxygen is low, below 3 mg/l, the water is called hypoxic. If all the dissolved oxygen is used up, below 0.5 mg/l, the water is called anoxic. Under hypoxic conditions, many marine plants and animals may not survive. No marine plants and animals that require oxygen can survive in anoxic conditions.Hope this helps.If any query please comment or inbox.