## Not used Half life

$\frac{d[R]}{dt}=-k; [R]=-kt + [R]_{0}; t_{\frac{1}{2}}=\frac{[R]_{0}}{2k}$

VivianaHF2L
Posts: 29
Joined: Fri Sep 28, 2018 12:20 am

### Not used Half life

In the 6th edition textbook, there is a table that describes all three orders but on the bottom of zero and second order the half life states not used. What does this mean?

Parth Mungra
Posts: 72
Joined: Fri Sep 28, 2018 12:28 am

### Re: Not used Half life

For zero order, there is no half life due to the integrated rate law not having concentration

DLee_1L
Posts: 103
Joined: Sat Aug 17, 2019 12:17 am

### Re: Not used Half life

Yeah, you cannot find a half life of a substance if its concentration does not affect the rate law to begin with. That would be the equivalent of taking half of 0.

Anika Chakrabarti 1A
Posts: 102
Joined: Sat Aug 24, 2019 12:17 am

### Re: Not used Half life

I thought that zero-order does have a half-life. In my notes, I have that it's [A]initial / 2k.

Louise Lin 2B
Posts: 97
Joined: Sat Aug 17, 2019 12:15 am

### Re: Not used Half life

the half-life of a zero-order reaction actually depends on the initial concentration and the rate constant

MinuChoi
Posts: 100
Joined: Wed Sep 18, 2019 12:15 am

### Re: Not used Half life

The half-life of a second-order reaction is t1/2=1/k[A0]

405268063
Posts: 102
Joined: Thu Jul 25, 2019 12:17 am

### Re: Not used Half life

Yes there is a half-life for zero order reactions and it is: [A initial] / 2k

Shrayes Raman
Posts: 129
Joined: Sat Jul 20, 2019 12:15 am

### Re: Not used Half life

Half life of zero order is[ initial concentration / 2 * k]

505306205
Posts: 97
Joined: Thu Jul 25, 2019 12:15 am

### Re: Not used Half life

The half-life for a first order reaction is used because it remains constant for a substance and is independent of reactant concentration.