Chemistry please help!
posted by Mary .
A Cesium 137 sample has a measured radioactivity of 50 microcuries.Cesium 137 has a halflife of 30 years.
How long will it take this sample to be reduced to a residual radioactivity of 6.25 microcuries?
Is there a formula to calculate half life?

k = 0.693/t_{1/2}
Then ln(No/N) = kt
No = 50 microcuries
N = 6.25 microcuries
k from above (t1/2 = 30 years).
t = solve for this. 
A 45 gram sample of a substance that's used to preserve fruit and vegetables has a kvalue of 0.1109.
Respond to this Question
Similar Questions

word problem
The half life of cesium137 is 30 years. Suppose we have a 10g sample. a)Find a function that models the mass remaining after t years. b)How much of the sample will remain after 80 years? 
chemistry
The isotype caesium 137, which has a half life of 30 years, is a product of nuclear power plants. How long will it take for the amount of this isotype in a sample of caesium to decay to onesixteenth of its original amount? 
Chemistry/math
Cesium137 has a halflife of 30 years. Suppose a lab stored a 30mCi sample n 1973. How much will be left in 2063? 
algebra
Suppose a sample of Cesium137 with initial mass of 200 grams decays to a mass of 160 grams voer the course of 10 years. Find the halflife of Cesium137 (Round to the nearest year) How much Cesium137 is left in the sample after 60 … 
chemistry
How long will it take for the 100mg of cesium137 to decay to 6.25mg(1/16 the original amount)? 
Science economic
Cesium 138 has a half life equal to 32.2 minutes. how long will it take for 2/4 of this sample to decay 
chem
Cesium137 has a half life of 30.0 years. If initially there are 8.0 kg of cesium137 present in a sample, how many kg will remain after 60.0 years? 
Calculuc
How do you set up this problem? The decay constant for the radioactive element cesium 137 is .023 when time is measured in years. Find its halflife. 
math
5. Cesium137 is a radioactive isotope. The following formula represents the remaining amount of a 300 gram sample of cesium137 in a storage tank after t years: N(t)=300e−0.02297t A) Determine the remaining amount of cesium137 … 
Chemistry
The cesium131 nuclide has a half life of 30 years. After 90 years, about 6g remain. What is the original mass of the cesium131 sample?