Half life


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Dakota_Campbell_1C
Posts: 51
Joined: Fri Sep 28, 2018 12:15 am

Half life

Postby Dakota_Campbell_1C » Fri Mar 15, 2019 1:55 am

Where does the 0.693 come from in the half life equation for first order reactions. Will that value ever change? I just want to know where it comes from and why we use it.

Samantha Silva 1F
Posts: 37
Joined: Tue Feb 13, 2018 3:00 am

Re: Half life

Postby Samantha Silva 1F » Fri Mar 15, 2019 2:08 am

It is the natural logarithm of 2.

Brandon Mo 4K
Posts: 70
Joined: Fri Sep 28, 2018 12:15 am

Re: Half life

Postby Brandon Mo 4K » Fri Mar 15, 2019 3:08 am

Using the integrated rate law of the first order reactions: ln [A] = -k t + ln [A]o, you can solve for the half-life (t1/2) by setting [A]= (1/2)[A]o.

Eventually you get, t1/2 = ln(2)/k or 0.693/k.

MadisonB
Posts: 63
Joined: Fri Sep 28, 2018 12:19 am

Re: Half life

Postby MadisonB » Fri Mar 15, 2019 4:13 am

After deriving the equation you are left with ln(2)/k.

Ricky Ma DIS 4E
Posts: 72
Joined: Fri Sep 28, 2018 12:27 am

Re: Half life

Postby Ricky Ma DIS 4E » Fri Mar 15, 2019 12:01 pm

What are the different kinds of answers that the half life equation can give us?


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