IB DP Chemistry D.6 Environmental impact of some medications HL Paper 3

Question

Distinguish between the hazards of high-level and low-level nuclear waste.

Answer/Explanation

Answer:

high-level has large amounts of «ionizing» radiation 

high-level has long half-lives
OR
high-level last longer/persists

Question

Technetium-99m is the most commonly used isotope for diagnostic medicine.
a. State the type of radiation technetium-99m emits.
b. Discuss the properties that make a radioisotope suitable for diagnosis.
c. Describe the proper disposal of low-level radioactive waste in hospitals.
d. 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.

▶️Answer/Explanation

Markscheme
a. gamma/ $\gamma$

b. Any three of:
«easily» detected/traced
OR
“gamma-radiation of approximately» same frequency as X-rays «so can be detected using existing X-ray equipment»
short/intermediate half-life «hence does not remain in body for long time»
weak ionizing radiation «less harmful»
OR
low amount of radiation produced «so less harmful»
OR
energy of photons is low
form «variety of» compounds that are absorbed by «different» organs
OR
«chemically» binds to many biologically active compounds
excreted quickly «from body»
c. store until material becomes inactive/radiation levels drop
dispose with other waste
OR
dispose in landfills
Only award M2 if M1 correct.
Accept “dispose by incineration” for M2.

d. Alternative 1 :
$$
\begin{aligned}
& « N=N_0(0.5) \frac{t}{t_{1 / 2}}=» 1.00 \times 10^{-11} \times(0.5) \frac{48.0}{6.03} \\
& « \mathrm{~N}=» 4.02 \times 10^{-14}\langle\mathrm{~mol} »
\end{aligned}
$$
Alternative 2:
$$
\begin{aligned}
& \ll \lambda=\frac{\ln 2}{6.03}=» 0.115 \ll \mathrm{hr}^{-1} » \\
& « N=N_0 e^{-\lambda t}=1.00 \times 10^{-11} \times e^{-0.115 \times 48}=» 4.01 \times 10^{-14}\langle\mathrm{~mol} »
\end{aligned}
$$
Award [2] for correct final answer.

 
 
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