Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Steve Vai on 03/09/2005 10:21:57
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im still at school, thus why i may ask simple/daft questions, but can you break down carbon dioxide into carbon and oxygen? because surely that would burn right?
"Turkeys killed my family" - Chip, 02/09/2005, 12:49
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You can but it would take at least as much energy as you would release by burning it...
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i see, good point, i shouldve thought about that, thanks
is there any catalyst to help the breakdown of those carbon dioxide, making it more effecient to burn?
"Turkeys killed my family" - Chip, 02/09/2005, 12:49
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Well, if you take a plant, you could break down CO2 into oxygen and a plant sugar (which contains a lot of carbon atoms). Burning CO2 would be very, very difficult, because normally CO2 is a product of burning. I´ll check out how to break down CO2 and get back on it.
[:P]
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cool
"Turkeys killed my family" - Chip, 02/09/2005, 12:49
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I have a similar energy making idea. I know that when you add conc. sulpuric acid to suggar it acts as a dehydrating agent and turns the sugar in to pure carbon giving off a lot off heat energy that could be converted in to something useful. Also the carbon could be burned to create even more energy.
Minerals are fun
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zirconium oxide electrolysis cell - i hear its possible to break it down using one of these, how would this work? it would be extrememly helpful if someone could explain why, the anode and cathode reactions would be nice too?
thanks
alex
"Turkeys killed my family" - Chip, 02/09/2005, 12:49
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Unfortuantely with energy, you never get anything for nothing, so you will allways have to put in as much energy as you get out - the plant does it by converting light energy into potential energy...
Remember the sulphuric acid takes energy to make...
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yeh, but if we have a constant source of power, say a turbine or solar cell, how would the electrolysis cell work? what are the reactions?
"Turkeys killed my family" - Chip, 02/09/2005, 12:49
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Start with the basic concept of free energy. This is the energy produced when two different atoms are brought together and form a molecule. General tables are usually available. So if Fe3O4 releases about 97 kcal per mole of energy and Al2O3 releases 253 kcal per mole, you can gain energy by reacting Iron Oxide with Aluminum and allowing the oxygen to move from the iron to the aluminum.
You can also go the other way where you add energy and seperate the aluminum from the aluminum oxide. This is generally done with electricity and the oxygen is reacted with graphite (carbon) to prevent it from going back and reforming with the aluminum. The amount of energy needed to liberate the aluminum is the 253 kcal minus inefficencies.
Early batteries were made with a copper plate, an iron plate and a copper sulfate solution. If you took electricty out of the device, you moved copper from the solution onto the iron plate. If you put electricity in, you reversed the process.
As you should know, we say there is no free lunch. What you make energy from was made with energy in the first place, so you are just consuming what others or other ages have stored. Sunlight is the main source of all energy on the earth (excepting nucelar which was once formed in a star). Now if they only had real sunlight in England.
David
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sulphuric acid could be collected from coal burning plants thus eleviating the demand for there creation.
Minerals are fun
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However concentrating the sulphuric acid would unfortunately use more energy than you got out :(
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I believe the sulfur is trapped by adding calcium to the combustion forming CaSO4 or calcium sulphate (gypsium). This is currently done in those plants that have been allowed to modernize. Many plants have choosen not to modernize because of the way the laws were written as an all or nothing step. Bush has relaxed some of the regulations to allow stepwise moderization, but the evniromentalists are howling.
I am not sure what they are comming up with to reduce Hg emmissions, but there are a lot of other souces of Hg emmissions besides coal plants that also need to be tackled.
David
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It's an important to recognise that a catalyst doesn't make a reaction "more efficient" - in the sense you meant it - but it does make a reaction easier. A catalyst allows a new mechanism in a reaction, so that the reaction occurs faster, or requires less energy to be put into the system as heat, it does not effect the final energy difference between reactants and products.
PS: "To burn" is to oxidise, ie. C or CO to CO2. To got the other way it to reduce, ie. CO2 to CO or C. Oxidation and reduction happen simultanenously in all balanced reactions, eg. C + O2 -> CO2, the oxygen in reduced and the carbon is oxidised. To make C from CO2 you could use the same logic and find a reactive metal that wanted the oxygen in CO2 more perhaps, Mg + CO2 + lots of heat -> MgO + CO. Difficult to go all the way to C by any such method though.
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Plants are our friends, To split CO2 requires about 95 kcal per mole.
David
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Hi, so say if I did have enough energy to split CO2 into Oxygen and a pure carbon form such as powder. How would I do it? [?]
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I have a similar energy making idea. I know that when you add conc. sulpuric acid to suggar it acts as a dehydrating agent and turns the sugar in to pure carbon giving off a lot off heat energy that could be converted in to something useful. Also the carbon could be burned to create even more energy.
Minerals are fun
Yes, in that process you have the release of some energy. My question is: why do you want to spend, let's say, 10 $ for an amount of sugar and H2SO4 that will release 0.01 $ of energy?
If you want a much less expensive process you can try this: go in the wood, take some little sticks, take them at home and burn them.
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Let's put it this way. If you could figure it out, you'd be rich. There's a lot of research being done in trying to convert CO2 (which is quite plentiful) into more useful forms of carbon. If this can be done, we can start making organic chemicals (including solvents, plastics, drug, etc.) without starting from fossil fuels.
Dick
Hi, so say if I did have enough energy to split CO2 into Oxygen and a pure carbon form such as powder. How would I do it? [?]
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Unfortuantely with energy, you never get anything for nothing, so you will allways have to put in as much energy as you get out - the plant does it by converting light energy into potential energy...
Remember the sulphuric acid takes energy to make...
Not exactly:
ΔHformation(SO3) = -395.77 kJ/mol
http://webbook.nist.gov/cgi/cbook.cgi?ID=C7446119&Units=SI&Mask=1#Thermo-Gas
and combining it with water to make H2SO4 releases further energy (ΔHreaction = -97.53 kJ/mol if I computed well from the ΔHf of the all 3 species).
Anyway, the process have a cost, is not inexpensive.
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Hi, so say if I did have enough energy to split CO2 into Oxygen and a pure carbon form such as powder. How would I do it? [?]
A very rough way should be to make it go through an electric arc, but you should find the exact process (temperature, speed of CO2 flux, ecc. ecc. Maybe you could improve the process efficiency if you found how to charge C and O atoms with opposite charges, so that to separate them with a magn. field to prevent them recombine immediately after splitting, of course all this in the void.)
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So is there away a of just making carbon powder from CO2?
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Yes, burn magnesium in CO2 and you get carbon.
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Could you split CO2 using a form of Electrolysis? sorry if this is a daft question. [???]
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Could you split CO2 using a form of Electrolysis? sorry if this is a daft question. [???]
That was pretty much what Alberto (Lightarrow) was suggesting with his arcing (might be easier to do with liquid CO2, but that would require great pressure to achieve).
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Why would you use energy to split CO2 just so that you can burn it for energy?Or why would you use energy produced somewhere else (meanwhile releasing CO2) just to split CO2? It sort of doesnt make sense if you look at it logically. and CO2 is a gas and a covalent molecule, how can you use electrolysis? Electrolysis only works on ionic compounds or (maybe charged compounds, not sure about this one).
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By burning CO2 do you mean with a naked flame like a fire? or could it be done like a electric heater? [?]
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I think they meant "Why would you use energy to split CO2 (to carbon and oxygen) just so that you can burn it (the carbon) for energy?"
CO2 doesn't burn (OK, it would in a room full of magnesium vapour or some such).
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Actually CO2 and water is in an equlibrium with H2CO3 - this is a part of an important system known as the carbonic acid system. One could, in theory, bubble atmospheric air through a column with water and thereby dissolving both the CO2 as aquatic CO2 and as carbonic acid. However, this obviously requires energy (as everything else).