Multiple Choice
The half-life of arsenic-74 is about 18 days. If a sample initially contains 5.13 x 104 mg arsenic-74, what mass (in mg) would be left after 80 days?
21. Nuclear Chemistry
Radioactive Half-Life
Back21. Nuclear Chemistry
Radioactive Half-Life
- Multiple Choice
What percentage of carbon – 14 ( t1/2 = 5715 years) remains in a sample estimated to be 18,315 years old?
- Open Question
What fraction of a reactant has been consumed after 4 half-lives in a first-order reaction?
- Open Question
What is the rate constant of a first-order reaction when 20.0% of a reactant remains after 30.0 s?
- Open Question
A fossil is found to have a 14C level of 76.0% compared to living organisms. How old is the fossil?
- Open Question
A moon rock collected by the Apollo mission is estimated to be 3.80 billion years old by uranium/lead dating. Assuming that the rock did not contain any lead when it was formed, what is the current mass of 206 Pb in the rock, given that it currently contains 1.180 g of 238 u? The half-life of 238U is 4.47×109 years.
- Multiple ChoiceA 2.00 mg sample of the radioisotope phosphorus-32 is found to contain 0.400 mg of phosphorus-32 after 33.3 days. Calculate the half-life (in days).
- Multiple ChoiceCarbon-14, which is present in all living tissue, radioactively decays via a first-order process. A one-gram sample of wood taken from a living tree gives a rate for carbon-14 decay of 13.6 counts per minute (CPM). If the half-life for carbon-14 is 5720 years, calculate the time it would take for the count rate to decrease to 6.8 CPM.
- Multiple ChoiceHow long will it take for 20% of the C-14 atoms in a sample of C-14 to decay, given that the half-life of C-14 is approximately 5730 years?
- Multiple ChoiceIf 60% of a radioactive isotope sample decays in 24 hours, what is its half-life?
- Multiple ChoiceThe accompanying graph illustrates the decay of ^{88}_{42}Mo, which decays via positron emission. What is the half-life of the decay?
- Multiple ChoiceThe half-life for the radioactive decay of C-14 is 5715 years and is independent of the initial concentration. How long does it take for 30.00% of the C-14 atoms in a sample of C-14 to decay?
- Multiple ChoiceThe half-life of Strontium-85 is 65 days. How much of an 80 mg sample is left after 260 days?