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Date	November 2016	Marks available	2	Reference code	16N.3.hl.TZ0.28
Level	HL	Paper	3	Time zone	TZ0
Command term	Deduce	Question number	28	Adapted from	N/A

Question

Technetium-99m is the most widely used medical radioisotope. It is usually made on-site in medical facilities from isotopes of molybdenum.

Deduce equations for the following nuclear reactions:

(i) Molybdenum-98 absorbs a neutron.

(ii) The isotope produced in (a) (i) decays into technetium-99m.

[2]

Molybdenum-99 has a half-life of 66 hours, while technetium-99m has a half-life of 6 hours. Outline why technetium-99m is made on-site.

[1]

Outline two reasons, other than its half-life, why technetium-99m is so useful in medical diagnosis.

[2]

Outline the nature of the radioactive waste that is generated by the use of technetium-99m in medical diagnosis.

[1]

Markscheme

${}_{{\rm{42}}}^{98}{\rm{Mo}}$ + ${}_{{\rm{0}}}^{1}{\rm{n}}$ → ${}_{{\rm{42}}}^{99}{\rm{Mo}}$

Accept ⁹⁸Mo + ¹n/n → ⁹⁹Mo.

${}_{42}^{99}{\text{Mo}} \to {}_{43}^{99\,{\text{m}}}{\text{Tc}} + {}_{ - 1}^0\beta$

Accept “ ${}_{ - 1}^0e$ ” for “ ${}_{ - 1}^0\beta$ ”.

Accept “ ${}^{99}Mo \to {}_{}^{99\,{\text{m}}}Tc + \beta$ ”.

Accept “ ${}_{ - 1}^0e/{e^ - }/e$ ” for “ $\beta$ ”.

Do not penalize “ ${}_{}^{99}Tc$ ” for “ ${}_{}^{99\,{\text{m}}}Tc$ ”.

molybdenum-99 can be easily transported «before it decays»/more stable
OR
«most of» technetium-99m will decay during transportation

Do not accept just “short half-life of Tc-99m”

emits gamma rays
OR
emissions escape from body
OR
emissions detected by gamma camera
OR
radiation dose is low

chemically reactive/versatile/transition metal bonds to a range of «biologically active» substances

Do not accept “short half-life of Tc-99m”.
Accept “energy of photons produced is «relatively» low” and “no high energy beta emission” for M1.
Accept “…has ability to form tracers” for “…bonds to a range of «biologically active» substances".

low-level «radioactive» waste/LLW
OR
small amounts of ionizing radiation for short time

Examiners report

[N/A]

Syllabus sections

Options » D: Medicinal chemistry » D.8 Nuclear medicine (HL only)

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17M.3.hl.TZ2.26a.ii:
Outline how the alpha-radiation in TAT is directed to cancer cells.
16N.3.hl.TZ0.28b: Molybdenum-99 has a half-life of 66 hours, while technetium-99m has a half-life of 6 hours....
16N.3.hl.TZ0.28c: Outline two reasons, other than its half-life, why technetium-99m is so useful in medical...
18M.3.hl.TZ1.19b:
Outline how Targeted Alpha Therapy (TAT) is used for treating cancers that have spread throughout the body.
17M.3.hl.TZ1.29a:
Yttrium-90 is used in treating certain cancers.

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20N.3.hl.TZ0.17d:
Technetium-99m has a half-life of $6.03$ hours. Calculate the amount of $1.00 \times 10^{- 11} mol$ of technetium-99m remaining after $48.0$ hours.
17M.3.hl.TZ2.26b.i:
Identify the type of radiation emitted by these two radioisotopes.
19M.3.hl.TZ1.24b(ii):
Outline the disposal of LLW.
19N.3.hl.TZ0.27a: State two common side effects of radiotherapy.
17M.3.hl.TZ2.26b.iii:
The half-life of lutetium-177 is 6.75 days. Calculate the percentage remaining after 27 days.
18N.3.hl.TZ0.22b.ii:
Suggest why the percentage of technetium-99m remaining in the human body two days after injection will be lower than that calculated in (b)(i).
18M.3.hl.TZ2.26a:
Phosphorous-32 undergoes beta decay. Formulate a balanced nuclear equation for this process.
17M.3.hl.TZ2.26a.i:
Explain why alpha-radiation is particularly suitable for this treatment.
19N.3.hl.TZ0.27b: Explain why technetium-99m is the most common radioisotope used in nuclear medicine.
17M.3.hl.TZ1.29c.i:
Calculate the rate constant, $\lambda$ , in day⁻¹, for the decay of iodine-131 using section 1 of the data booklet.
17M.3.hl.TZ2.26b.ii:
State an equation for the one-step decay of yttrium-90.
19N.3.hl.TZ0.27c:
25.0 μg of iodine-131, with a half-life of 8.00 days, was left to decay.

Calculate the mass of iodine-131, in μg, remaining after 32.0 days. Use section 1 of the data booklet.
17N.3.hl.TZ0.21b:
The half-life of lutetium-177 is 6.73 days. Determine the percentage of a sample of lutetium-177 remaining after 14.0 days.
18M.3.hl.TZ2.26b:
The half-life of phosphorus-32 is 14.3 days. Calculate the mass, in g, of ³²P remaining after 57.2 days if the initial sample contains 2.63 × 10⁻⁸ mol. Use table 1 of the data booklet and M_r = 31.97 g mol⁻¹.
19M.3.hl.TZ1.24a(i):
Determine the percentage of technetium-99m remaining after 24.0 hours.
19M.3.hl.TZ2.26a:
Evaluate the suitability of technetium-99m for this use.
18M.3.hl.TZ1.19a:
Describe how ionizing radiation destroys cancer cells.
18N.3.hl.TZ0.22a:
Alpha particles are more damaging to human cells than any other nuclear radiation and yet they are used in targeted alpha therapy (TAT).

Explain how TAT is relatively safe to use in the treatment of dispersed cancers.
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Calculate the time, in days, for 90% of the sample to decay.
18M.3.hl.TZ2.26c:
Explain the targeted alpha therapy (TAT) technique and why it is useful.
19M.3.hl.TZ2.26b:
Calculate the percentage of technetium-99m remaining after 10.0 hours. Use section 1 of the data booklet.
17N.3.hl.TZ0.21a:
State a nuclear equation to show the decay of lutetium-177.
19M.3.hl.TZ1.24a(ii):
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19M.3.hl.TZ1.24c:
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Suggest why MRI is much less dangerous than imaging techniques such as X-rays and radiotracers. Use section 3 of the data booklet.
18N.3.hl.TZ0.22b.i:
Technetium-99m ( ${}_{43}^{99{\text{m}}}{\text{Tc}}$ ) has a half-life of 6.0 hours. Calculate the percentage of ${}_{43}^{99{\text{m}}}{\text{Tc}}$ remaining in a sample of the radioisotope after two days.
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20N.3.hl.TZ0.17a:
State the type of radiation technetium-99m emits.

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