Question

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 nuclei and zero 15N nuclei. How many 15O nuclei remain after 122 s has passed?

How many 15N nuclei are there after 122 s has passed?

How many 15O nuclei remain after 244 s has passed?

How many 15N nuclei are there after 244 s has passed?

Suppose you start with 7.86×103 Carbon-14(14C) nuclei. 14C has a half-life of 5730 years and decays into Nitrogen-14(14N) via a beta decay. How much time has passed if you are left with 3.93×103 14C nuclei? (The units for years is 'yr'.)

How much time has passed if you are left with 1.96×103 14C nuclei?

Answer #1

Q1. Carbon-14 – or 14C – is a radioactive isotope of carbon with
a half-life of 5,730 years. It decays into nitrogen-14 – or 14N – ,
which is a stable isotope of nitrogen.
(a) Which of the three nuclear decay processes describes the decay?
Explain. (Hint: You can get the atomic number of carbon and
nitrogen from a periodic table.)
(b) Write down the equation for the decay.
(c) What is the decay constant for 14C?
All isotopes of...

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?

A sample of radioactive nuclei initially contains 6.00
×1010×1010 radon atoms. The half-life of this type of nucleus is
500 days. How many nuclei have decayed after 167 days?
A sample of radioactive nuclei initially contains
6.00 radon atoms. The half-life of this type of nucleus
is 500 days. How many nuclei have decayed after 167 days?
2.00×1010
4.00×1010
1.24×1010
4.76×1010

The radioactive isotope 234Pa has a half-life of 6.70
h. A sample containing this isotope has an initial activity
(t = 0) of 35.0µCi. Calculate the number of nuclei that
decay in the time interval between t1 = 7.0 h
and t2 = 14.0 h.
___________ Nuclei

A certain radioactive element has a half-life of 6.93 s. If
there are initially 1.00 x 103 nuclei of that element,
how many are left after 7.00 s? Give your answer to 2 significant
figures.

The radioactive isotope 198Au has a half-life of 64.8 hours. A
sample containing this isotope has an initial activity at (t=0) of
1.50e-12 Bq. Calculate the number of nuclei that will decay in the
time interval between t1=10 hours and t2=20 hours
Answer is 4.60e16 but I'm not sure how. Thanks and please show
work

The
radioactive isotope Gold-198 has a half-life of 64.80 hrs. A sample
containing this isotope has an initial activity of 40.0 μCi.
Calculate the number of nuclei that will decay in the time interval
from 10 hrs to 12 hrs.[10 marks]

A sample of radioactive nuclei initially contains 9.00 ×1010
radon atoms. The half-life of this type of nucleus is 450 days. How
many nuclei have decayed after 150 days?
OPTIONS:
7.14×1010
6.00×1010
3.00×1010
1.86×1010

The radioactive isotope 198Au has a half-life of 64.8 hr. A
sample containing this isotope has an initial activity (t = 0) of
1.5x 10^12 Bq. Calculate the number of nuclei that decay in the
time interval between t1 = 10 hr and t2 = 12 hr.
Please show and explain work, and do not use calculus to solve
it.

A radioactive isotope has a half-life of 72.0 min. A sample is
prepared that has an initial activity of 1.40×1011
Bq.
Q1: How many radioactive nuclei are initially present in the
sample?
Q2: How many are present after 72.0 min?
Q3: What is the activity after 72.0 min?
Q4: How many are present after 144 min?
Q5: What is the activity after 144 min?

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