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/cm
3 or mol/L)
k for your reaction can be found at:
NIST Kinetics Database- 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