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Posted by **Jazmin** on Monday, May 30, 2011 at 8:52pm.

a.10 min

b.20 min

c.30 min

d.40 min

the answer is a.10 min but i would like to know why, please help.

- Chemistry -
**DrBob222**, Monday, May 30, 2011 at 10:21pmln(No/N) = kt

No = 80 mg

N = 10 mg

t = 30 min

solve for k, then

k = 0.693/t_{1/2}

Substitute k from above and solve for t_{1/2}

10 min is correct.

- Chemistry -
**shemelis**, Tuesday, October 2, 2012 at 3:33am10 minute is correct

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