Page 1 of 1

### Half Lives?

Posted: Fri Mar 09, 2018 8:52 am
Is it accurate to use half lives for questions that say something like 1/4 of the reactant is remaining?

### Re: Half Lives?

Posted: Fri Mar 09, 2018 9:00 am
Yes because that would indicate that the species has undergone two half-lives.

### Re: Half Lives?

Posted: Fri Mar 09, 2018 12:14 pm
In general, at any stage of the reaction, we can find how much of a reactant is remaining after n half-lives by (1/2)^n [A]0. Thus, if 1/2 is a factor of the remaining amount, then it is allowed to use the half life method.

### Re: Half Lives?

Posted: Fri Mar 09, 2018 12:18 pm
Yes, you would simply calculate the half life and then multiple it by 2 get the time to reach 1/4 of the reactant remaining.

### Re: Half Lives?

Posted: Sat Mar 10, 2018 10:17 pm
yes because 1/4th product is = the amount left after two half lives

### Re: Half Lives?  [ENDORSED]

Posted: Sat Mar 10, 2018 10:56 pm
Yes, because you would be able to multiply the half-life by the number of times it occurred to find the time it would take to reach the new concentration.

### Re: Half Lives?

Posted: Mon Mar 12, 2018 6:05 pm
yes, because 1/4 is the half life of the half life.

### Re: Half Lives?

Posted: Mon Mar 12, 2018 10:19 pm
Yes, half-life works for that fraction.