Posted by koteswaramma on Friday, August 15, 2014 at 9:22am.
a radioactive substance decays 10% in 5 days. The amount remains after 20 days?

chemistry  DrBob222, Friday, August 15, 2014 at 2:20pm
You need to determine k, the rate constant and I would do it this way.
ln(No/N) = kt
No = 10
N = 90
k = solve for this
t = 5 days.
Then knowing k, redo
ln(No/N) = kt
No = 100
N = Solve for this.
k from above
t = 20 days

chemistry  Anonymous, Sunday, September 11, 2016 at 8:56am
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