[soupastupid]

for a 2nd order half life, the higher concentration of reactant i start with, the shorter the half life??

concentration is different from the amount?
so if it were the amount ...

more amount of reactant means longer half life?

[enahs]

half-life is completely independent of concentration/amount.

It does not matter how much you have, weather 10000000000000 kg of 0.00000000001mg of some substance, if they are the same substance they have the same half-life.

[Cauchy]

half-life is completely independent of concentration/amount.

It does not matter how much you have, weather 10000000000000 kg of 0.00000000001mg of some substance, if they are the same substance they have the same half-life.

That is only true for a first order process (chemical reaction in this case).

[Jorriss]

for a 2nd order half life, the higher concentration of reactant i start with, the shorter the half life??

concentration is different from the amount?
so if it were the amount ...

more amount of reactant means longer half life?

For a second order reaction, assuming constant volume, more moles or higher concentration leads to a shorter half life.