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### Half-life of first order reactions

Posted: Wed Feb 28, 2018 7:40 am
I understand from the half-life equation that the half-life of a first order reaction does not depend on concentration and that, therefore, it has the same value at all stages of the reaction. However, this does not make sense to me. How can the half-life be the same at all stages of the reaction, even if the concentration changes?

### Re: Half-life of first order reactions

Posted: Wed Feb 28, 2018 8:05 am
To my understanding, half-life doesn't change because the rate it's getting rid of a substance is proportional to the amount. So, if there's more of a substance then it'll dissipate at a faster rate. Zero-order reaction, on the other hand, I think eliminates a given amount of a substance at intervals, which is why it's half-life would change if you change the amount of substance there is.

Hopefully, I'm not getting this all wrong. X)

### Re: Half-life of first order reactions

Posted: Sun Mar 04, 2018 5:24 pm
The half-life of a substance is the time needed for its concentration to fall one-half its initial value. It doesn't depend on concentration.

### Re: Half-life of first order reactions

Posted: Sun Mar 04, 2018 5:40 pm
The half life of any substance would be the time required for the substance to decay to half it's original value.

### Re: Half-life of first order reactions  [ENDORSED]

Posted: Mon Mar 05, 2018 1:46 pm
Half-life represents the time that a material is decayed to half of its original content. This variable is actually independent of the concentrations. More specifically, the time a given material decays from its original content to half of it is the same as that used to decay from half of it to a quarter of it.