exponential decay

[505095793]

Why do reactions slow as time goes on? Would a reaction still slow if we had excess reactants?

[405112316]

Rate laws are usually directly dependent on the amount of reactants, so if the reactants are lower, the rate law will be lower.

[Luc Lorain 1L]

It all depends on our understanding of half life. Half life, as you know, is the time it takes for 50% of a sample to decay or otherwise react. As we progress through time, the mass/concentration of the sample decreases rapidly, until only a very small amount is left. The decay follows asymptotic behavior at this point; it will always try to decrease by a factor of 1/2, and theoretically never reach zero.