## 1/2 life

$\frac{d[R]}{dt}=-k[R]; \ln [R]=-kt + \ln [R]_{0}; t_{\frac{1}{2}}=\frac{0.693}{k}$

Tatum Keichline 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:26 am

### 1/2 life

Does the 1/2 life for first order depend on the initial concentration like it does for zero and second-order reactions?

David Effio 1H
Posts: 38
Joined: Wed Feb 14, 2018 3:01 am

### Re: 1/2 life

No, if you look at the equation, the half-life only takes into account the rate constant, which is dependent on temp and activation energy only.

Rachel-Weisz3C
Posts: 66
Joined: Fri Sep 28, 2018 12:23 am

### Re: 1/2 life

1/2 life for first order is the only order that is not dependent on initial concentration but just the reaction constant (k), with units 1/s.

Danielle_Gallandt3I
Posts: 70
Joined: Fri Sep 28, 2018 12:24 am

### Re: 1/2 life

No, based on the half-life equations it is not affected by initial concentration, only the rate constant. This means that the half life is actually more dependent on other factors, such as temperature

SydBenedict2H
Posts: 60
Joined: Wed Nov 08, 2017 3:00 am

### Re: 1/2 life

Why is it that for only the first order it isn't dependent on the initial concentration?

Raj_Bains_2C
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### Re: 1/2 life

The half-life for first order dow not depend on the initial concentration.

Raj_Bains_2C
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### Re: 1/2 life

Raj_Bains_2C wrote:The half-life for first order dow not depend on the initial concentration.

*does not*

Casandra
Posts: 65
Joined: Fri Sep 28, 2018 12:17 am

### Re: 1/2 life

The 1/2 life for a first order does not depend on the initial concentration.