Chemistry
posted by Jennifer .
Tc99 is a radioactive isotope that decays by beta emission and is used by radiologists in the diagnosis of liver disease. Its decay behavior is shown by the activitytime table. What is its halflife?

You are supposed to look at the table and use the data to calculate the half life. How do you suppose we can do that if you don't show the table?

The table wasn't available

counts/min time(hours)
800 0
713 1
450 5
200 12
112 17
a. 5h
b. 6h
c. 12h
d. 99h 
ln(No/N) = kt
No = 800 in all cases.
N = values from table
k = solve for this
t = time in hours.
For example, the first one is
ln(800/713) = k(1 hour)
k = 0.115 if I didn't goof.
Do that for each time period and average the values. Then substitute into the following:
k = 0.693/t_{1/2} and solve for t_{1/2}.