Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: ifuller on February 09, 2008, 11:50:15 AM
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Does anyone know a formula to calculate the approximate time that it would take for two mono-atomic elements (ie. H + H) to form H2. I know that the time will be very short but are we talking microseconds or tenths of a second. Thanks for anyone who can help.
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No idea about the formula, but think for a moment. If they are a mile apart, it will take forever. If they are at the distance they are in the molecule, reaction will be almost instant.
Is your question well defined?
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That is a good point that I didn't address. The reason I ask is I am interesting in splitting H2 into H and H and then using those molecules to react with other chemicals. I am trying to figure out if this is possible. Thanks for the input though.
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Starting from molecular H2 requires drastic conditions, but you can easily create hydrogen in statu nascendi by the reaction of metals with acid... For what kind of reactions do you need it?
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I am experimenting with reactions in which a reactant combines with hydrogen only under extreme conditions. I am planning on using a heated tungsten filament to split H2 into atomic hydrogen. I then hope to react that atomic hydrogen with the other reactant to create the same products with much lower energy requirements.
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Like Borek said, it's going to depend on how much H. you have there. The number density is what will tell you how long the H. will last:
Rate constant for the reaction: H + H --> H2
Rate (of formation of H2) = k[H][H]
where [ ] is the number density (molecules/cm3 or mol/L)
k for your reaction can be found at: NIST Kinetics Database (http://kinetics.nist.gov/kinetics/ReactionSearch?r0=12385136&r1=12385136&r2=0&r3=0&r4=0&p0=1333740&p1=0&p2=0&p3=0&p4=0&)
- Just like all rate constants it depends on temperature...but you can make an approximation :)
Last thing: Be careful, radicals have a tendency to react with lots of stuff :)