Question

Suppose we have 50 Kilograms of some radioactive compound that has a half-life of 5000 years. How long (round to the nearest year) will it take for the radioactive compound to decay to 2 kg?

Answer #1

1. The half-life single radioactive nuclei is 10 years. When
will this nuclei decay?
2. The half-life of radioactive nuclei is 20 years. How much
time must pass before 50% of the nuclei have decayed? _____75
years?

The half-life of the radioactive material cesium-137 is 30
years. Suppose we have a 180-mg sample.
(a) Write a formula that gives the mass that remains after
t years. (Round the relative growth rate to four decimal
places.)
A(t) =
(b) How much of the sample remains after 100 years? (Round your
answer to two decimal places.)
mg
(c) After how long will only 1 mg remain? (Round your answer to one
decimal place.)
years
(d) At what rate is...

15.58 The half-life for the radioactive decay of C−14 is 5730
years. How long will it take for 25% of the C−14 atoms in a sample
of C−14 to decay? If a sample of C−14 initially contains 1.9 mmol
of C−14, how many millimoles will be left after 2250 years?

The half-life for the radioactive decay of C−14 is 5730
years.
Part A: How long will it take for 25% of the C−14 atoms in a
sample of C−14 to decay?
Part B: If a sample of C−14 initially contains 1.9 mmol of C−14,
how many millimoles will be left after 2255 years?

You have a sample of a radioactive material with a half-life of
5.0 years that has a current activity of 0.12 µCi.
The sample has a label on it which indicates that when it was
first manufactured it had an activity of 3.84 µCi.
How long ago was the sample manufactured? (to 2 s.f and in
years)

The half-life for the radioactive decay of U−238 is 4.5 billion
years and is independent of initial concentration.
A) How long will it take for 10% of the U−238 atoms in a sample
of U−238 to decay?
Express your answer using two significant figures.
B) If a sample of U−238 initially contained 1.4×1018
atoms when the universe was formed 13.8 billion years ago, how many
U−238 atoms will it contain today?
Express your answer using two significant figures.

Hydrogen-
3
is radioactive and has a half life of
12.3
years. What percentage of a sample would be left after
53.3
years?
Round your answer to
2
significant digits.
Hydrogen-
3
is radioactive and has a half life of
12.3
years. What percentage of a sample would be left after
53.3
years?
Round your answer to
2
significant digits.

15.57 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? Express your answer using two significant figures. If a
sample of U−238 initially contained 1.1×1018 atoms when the
universe was formed 13.8 billion years ago, how many U−238 atoms
will it contain today? Express your answer using two significant
figures.

The half-life of a radioactive isotope represents the average
time it would take half of a collection of this type of nucleus to
decay. For example, you start with a sample of 1000 Oxygen-15 (15O)
nuclei, which has a half-life of 122 seconds. After 122 seconds,
half of the 15O nuclei will have decayed into Nitrogen-15 (15N)
nuclei. After another 122s, half of the remaining Oxygen nuclei
will have also decayed, and so on. Suppose you start with 4.00×103
15O...

The radioactive decay of I-131 is first order with a half life
of 8.02 days. How long will it take for 80% of a sample to decay?
The answer is 19 days. I need help working it out to get that
answer. Thank you in advance.

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