21. Nuclear Chemistry

Rate of Radioactive Decay

객관식
How many mg of a 3.50-mg sample of Tc-99 will remain after 4 half-lives have passed?
998
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객관식
During World War I radium-226 was used in the manufacturing of luminous paint. If it takes 2.12 × 10⁴ days for its degradation to be 2.49% complete, what is its decay constant?
761
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3
rank
객관식
The half-life for the radioactive decay of U-238 is 4.5 billion years and is independent of initial concentration. How long will it take for 20% of the U-238 atoms in a sample of U-238 to decay?
379
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객관식
A sample of Th-219 requires 3.84 × 10⁻⁶ seconds to decay to 1.50 mg. What was the initial mass of the sample of Th-219? (t_1/2 for Th-219 = 1.05 × 10⁻⁶ s)
978
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객관식
If the decay constant for polonium-209 is 6.80 × 10^-3 yrs^-1, what fraction of it remains after 1.1 × 10⁴ years?
853
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2
rank
객관식
For the radioactive decay of lead-202 the decay constant is 1.32 × 10^-5 yr^-1. How long will it take in hours to decrease to 53% of its initial amount?
830
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객관식
Carbon-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. If the half-life for carbon-14 is 5720 years, what is the age of a sample that has a decay rate of 6.8 counts per minute?
528
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미해결 질문
A fossil is found to have a ¹⁴C level of 85.0% compared to living organisms. How old is the fossil?
735
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객관식
Estimate the half-life of the isotope from the graph below.
1510
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객관식
How long will it take for 80% of a 1.20-mg sample of Rn-220 to decay? The half-life of Rn-220 is 55.6 s.
1013
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