<PRE><B>Question 173430</B>
The decay rate of krypton-85 is 6.3% per day.  What is the half-life?
Using the exponential decay function P(t) =Po^e^-kt
:
The exponential decay formula that I am familiar with:
A = Ao[2^(-t/h)]
where
Ao is the initial amt
A = final amt
t = time
h = half-life of the substance
:
Assume Ao = 100, Assume t = 1 day, find h (half life in days)
After 1 day, A = 100 - 6.3 = 93.7
:
100 * 2^(-1/h) = 93.7
:
2^(-1/h) = {{{93.7/100}}}
:
2^(-1/h) = .937
:
ln[2^(-1/h)) = ln(.937)
:
{{{-1/h}}}*.693 = -.065
:
{{{-.693/h}}} = -.065
:
h = {{{(-.693)/(-.065)}}}
h = 10.66 days is the half life of krypton-85 according to this information
:
In actual fact I think they mean 6.3% per year, hence, 10.66 yrs half life </PRE>