## Half-Life 1st Order Reaction

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

Olivia Young 1A
Posts: 60
Joined: Fri Sep 28, 2018 12:24 am

### Half-Life 1st Order Reaction

Is the equation t1/2 = 0.693/k valid for all first order reactions? And if so, it it because the initial concentration of A cancel out and leave ln(1/2)?

Dimitri Speron 1C
Posts: 60
Joined: Fri Sep 28, 2018 12:17 am
Been upvoted: 1 time

### Re: Half-Life 1st Order Reaction

Yes, that's exactly correct.

Megan_Ervin_1F
Posts: 78
Joined: Fri Sep 28, 2018 12:18 am

### Re: Half-Life 1st Order Reaction

Also remember that you can always derive this equation it you have any doubts

Erin Kim 2G
Posts: 75
Joined: Fri Sep 28, 2018 12:26 am

### Re: Half-Life 1st Order Reaction

For the first order
the half life equation is t(1/2)= ln2/k.
It is applicable to all first order rate reactions.

Annalyn Diaz 1J
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am

### Re: Half-Life 1st Order Reaction

Why is it that the half-life of a first order reaction doesn't depend on initial concentration?

Nicholas Le 4H
Posts: 74
Joined: Fri Sep 28, 2018 12:24 am

### Re: Half-Life 1st Order Reaction

Yes, it is applicable to all first order rate reactions.

Amy Dinh 1A
Posts: 62
Joined: Fri Sep 28, 2018 12:23 am

### Re: Half-Life 1st Order Reaction

The initial concentration gets cancelled out when you derive the equation. Thus you end up with the equation t1/2 = 0.693/k