Posted by **Sara** on Friday, June 28, 2013 at 4:30pm.

The half-life for the second-order reaction of a substance A is 58.2 s when A0 = 0.63 mol L-1 Calculate the time needed for the concentration of A to decrease to the following values.

(a) one-third of its original value

(b) one-sixth of its original value

(c) one-seventh of its original value

- Chemistry -
**DrBob222**, Friday, June 28, 2013 at 6:06pm
What's wrong with substituting values into the second order equation and solving for time.

Could it be you don't know how to handle 1/3, 1/6, 1/7 th values?

If Ao = 0.63 then 1/3 that = ? for a; 1/6 that for b and 1/7 that for c.

- Chemistry -
**Sara**, Friday, June 28, 2013 at 6:22pm
I don't understand how to figure out K.

I used the information in the problem given to solve for k, and then plug that k in to solve for t, but it's not the correct answer.

- Chemistry -
**DrBob222**, Friday, June 28, 2013 at 6:45pm
t_{1/2} = [1/k(Ao)]

- Chemistry -
**Sara**, Friday, June 28, 2013 at 6:48pm
I understand, but what is K or how can I determine K?

- Chemistry -
**DrBob222**, Friday, June 28, 2013 at 8:08pm
The problem GIVES you the half life. Use that and the equation I provided above to determine k.

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