Assume you have such a watch. If a minimum of 18.0% of the original tritium is needed to read the dial in dark places, for how many years could you read the time at night?  Assume first-order kinetics.

[References] Use the References to access important values if needed for this question. The half-life of the radioactive isotope phosphorus-32 is 14.3 days. How long will it take for the mass of a sample of phosphorus-32 to decay from 61.3 micrograms to 15.3 micrograms? days

What is the half-life (seconds) of a reaction that has a rate constant, k = 0.00554 M/s where the initial concentration is 0.712 M? Report your answer to the tenths place and do not include units.

Geologists can estimate the age of rocks by their uranium-238 content. The decay of U-238 is first-order with a half-life of 4.5 billion years (4.5×109 yrs). A rock contains 47.3% of the initial amount of U-238 from when it was formed. How old is the rock?

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How long would it take in minutes,  for the amount of potassium -44 to decrease from 80.0 to 10.0mg

Phosphorous-32 (black dot) decays by beta emission to form sulfur-32(white dot). How many half-lives have passed in the reaction shown?       Need more information to determine     1     4     3     2

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The radioactive isotope 99mTc (used in medical stress tests) decays via gamma emission following first order kinetics and has a half-life of 6.02 hours. How long will it take before the radioactivity drops below 5.00% of the initial value?   A.  42.1 hours B.  30.2 hours C.  26.1 hours D.  24.1 hours

Fallout from nuclear weapons tests in the atmosphere is mainly 90Sr and 137Cs , which have 28.6- and 32.2-y half-lives, respectively. Atmospheric tests were terminated in most countries in 1963, although China only did so in 1980. It has been found that environmental activities of these two isotopes are decreasing faster than their half-lives. Why might this be?