You can only unlock the chapter using a special code that we will send you via the Viber app. Receiving a message is free of charge and with no obligations.
My phone number:
Get a code
In compliance with the law, persons under the age of 15 can enter their phone number only in the presence of a parent or guardian.
4-character (Viber) code:
Check the received code
The page will be refreshed automatically in a few seconds.
To ensure the proper functioning of the website, OpenProf uses cookies that do not store personal data. By continuing to use the website, you agree to cookies. Tell me more »
per cubic metre of air.
.
of atmospheric air contains 
molecules. Calculate the ratio
nuclei at time 
. At time 
, it contains 
nuclei of the isotope. For the period 
, state, in terms of 
and 
. The uncertainty in the calibration is 
. Calculate the length of time, in days, after the calibration has been made, for the stated activity of 
.
) undergoes 
-decay to form sulfur-33 (
), which is stable. The half-life of phosphorus-33 is 24.8 days.
.
. Calculate
-particles. A sample of americium-241 of mass 
is found to have an activity of 
.
and the half-life 
of an isotope are related by the expression
is related to the half-life 
by the expression
). A cobalt-60 source for use in a school laboratory has an activity of 
. Calculate the mass of cobalt-60 in the source.
. Determine, for the strontium-89 source at the time that it was prepared,
) is unstable and undergoes alpha decay.
of plutonium-238. Each nucleus of plutonium-238 that decays emits 
of energy. The half-life of plutonium-238 is 87.7 years.
of nuclei of plutonium-238 in the power source.
of its initial value. Calculate the time, in years, for which the space probe will function.
) decays by alpha emission to form a stable isotope of lead (Pb).
of the number of unstable nuclei 
in a sample of polonium-211 is shown in the graph below.
, the sample contains only polonium-211.
of polonium-211. Give a unit with your answer.
.
, the total amount of energy given to alpha particles that are emitted between time 
and time 
.
). The activity of the iodine-131 in 
of this water is 
. The half-life of iodine-131 is 8.1 days.
of water has a mass of 
. Calculate the ratio
. Calculate the time, in days, for the activity of the contaminated water to be reduced to this acceptable level.
) is an unstable nuclide. The activity of a sample of 
of strontium-90 is 
.
of strontium-90.
. Suggest a possible reason for this.
, a sample of a radioactive isotope contains 
nuclei. In a short time 
, the number of nuclei that decay is 
. State expressions, in terms of the symbols 
),
is related to the half-life 
of a radioactive isotope by the expression
) has an initial activity of 
. Sodium-24, of half-life 15 hours, decays to form a stable daughter isotope. All of the solution is poured into a container of water. After 36 hours, a sample of water of volume 
, taken from the container, is found to have an activity of 
. Assuming that the solution of the radioactive isotope is distributed uniformly throughout the container of water, calculate the volume of water in the container.
−particle and a 
-ray photon. The count rate produced from a sample of the isotope copper-66 is measured using a detector and counter, as illustrated in the figure below.
to 
. Calculate the half-life of copper-66.
of the number 
of technetium-101 nuclei in a sample of radioactive material is shown in the figure below.
, of the sample of technetium-101 at time 
. Show your working.
of technetium-101.
) is produced in the upper atmosphere and then sinks down onto the Earth’s surface. Nuclei of beryllium-7 decay with a half-life of 53.3 days to form stable nuclei. The activity of a sample of beryllium-7 on a tree leaf is 
.
.
.
and decays to form a nuclide D. This nuclide D is unstable and decays with decay constant 
to form a stable nuclide S. The decay chain is illustrated in the figure below.
of the number of nuclei of each of the three nuclides in the sample is shown in the graph below.
, of this nuclide.
. The decay chain of a different nuclide E is illustrated in the figure below.
of nuclide F is very much larger than the decay constant 
of nuclide E. By reference to the half-life of nuclide F, explain why the number of nuclei of nuclide F in the sample is always small.
. The graph below shows the variation with 
of the numbers of nuclei of X and of Y as the sample decays.
at time 
nuclei of the isotope at time 
. At time (
), the sample contains (
) nuclei of the isotope. The time interval 
is short. Use the symbols 
, 
and 
of the isotope.
) is radioactive and decays to form lead-204 (
). The nuclear equation for this decay is
, of the mass
, released.
nucleus (
-particle) is found to be less than the energy calculated in (i) part 2. Suggest two possible reasons for this difference.
. Determine the activity of the isotope X in the sample after a time of 2.0 hours.
