Question

Iodine-131 is an isotope of iodine (Z = 53) used for the treatment of hyperthyroidism, as it is readily absorbed into the cells of the thyroid gland. With a half-life of 8 days, it decays into an excited Xenon-131 atom (Z = 54).

1.What type of radioactive decay occurs in this process?

a. alpha decay

b. electron capture

c. gamma decay

d. beta decay

2. The related isotope iodine-125 is used in brachytherapy. In what way does it differ from iodine-131?

a. The number of beta particles

b.The number of neutrons

c.The number of electrons

d.A different number of protons

3.Which of the following is a true statement regarding the atomic mass during the decay from iodine-131 to xenon-131?

a. We expect the mass has decreased because xenon-131 has one less proton

b. We expect the mass has decreased because xenon-131 has one more proton.

c. We expect the mass has increased because xenon-131 has an extra proton.

d. We expect the mass has increased because xenon-131 has one less proton

4. What percentage of an iodine-131 sample remains after 44 days?

a. 50%

b. 88%

c. 2.2%

d. 3.1%

5. The SI unit for activity (decays per second) is the Becquerel (Bq). A hospital receives a shipment of iodine-131 with an activity of 8 × 1010 Bq. After 16 days, there are several patients that need to be given doses of 1 × 109 Bq each. How many patients can be treated?

a. 10 patients

b. 20 patients

c. 40 patients

d. 80 patients

Answer 1

1.What type of radioactive decay occurs in this process?

Solution: The atomic number of xenone is 54. so there is an increase in number of protons in the decay product.

so it is undergoin

d. beta decay

2. The related isotope iodine-125 is used in brachytherapy. In what way does it differ from iodine-131?

The atomic number of isotopes remain the same the difference is in mass number due to difference in

b.The number of neutrons

3.Which of the following is a true statement regarding the atomic mass during the decay from iodine-131 to xenon-131?

b. We expect the mass has decreased because xenon-131 has one more proton.

4. What percentage of an iodine-131 sample remains after 44 days?

Half life = 8 days

K = 0.693 / t_1/2 = 0.693 / 8 = 0.087 days-1

ln [At / A0] = -kt

ln [At / A0] = -0.087 X 44 = -3.812

Taking antilog

[At / A0] = 0.0221

At = 0.0221 [At]

% remained = 2.2%

5. The SI unit for activity (decays per second) is the Becquerel (Bq). A hospital receives a shipment of iodine-131 with an activity of 8 × 1010 Bq. After 16 days, there are several patients that need to be given doses of 1 × 109 Bq each. How many patients can be treated?

we know that

ln [At / A0] = -kt and t = 16 days

ln [At / A0] = -1.386

[At / A0] = 0.25

A0 = 8 x 10^10

At = 0.25 X 8 x 10^10 = 2 x 10^10

the activity that remains after 16 days is 2 x 10^10 Bq

number of patients that can treated = activity / dose

dose = 1 x 10^9

number of patients that can treated = 2 X 10^10 / 10^9 = 20

a. 10 patients

b. 20 patients

c. 40 patients

d. 80 patients