Exercise 19.48 At 8:00 A.M., a patient receives a 56 mg dose of I131 to obtain a

Question

Exercise 19.48

At 8:00 A.M., a patient receives a 56 mg dose of I131 to obtain an image of her thyroid.

Part A

If the nuclide has a half-life of 8 days, what mass of the nuclide remains in the patient at 5:00 P.M. the next day?

Express your answer using two significant figures.

NOT 55

Exercise 19.48

At 8:00 A.M., a patient receives a 56 mg dose of I131 to obtain an image of her thyroid.

Part A

If the nuclide has a half-life of 8 days, what mass of the nuclide remains in the patient at 5:00 P.M. the next day?

Express your answer using two significant figures.

NOT 55

Explanation / Answer

time taken,
t = 24+ 9 =33 hours

half life = 8 days = 8*24 hour= 192 hr

rate constant,
k = 0.693/half life
= 0.693 / (192)
= 3.61*10^-3 hr-1

now use:
[R] = [R]o*e^(-k*t)
= 56*e^(-3.61*10^-3 * 33)
= 50 mg
Answer: 50 mg

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