Question

A patient is given 40.00 mg of iodine-131 (131I ) 131 53
The half-life of 53 I is 8 days.
How many milligrams of the 131I remains in the
patient after 32 days?

Answer 1

Answer:

2.5 mg

Explanation:

We are given;

• Original mass of I-131 is 40.0 mg
• Half life of I-131 is 8 days
• Number of days 32 days

We are required to determine the mass that will remain;

• Using the formula;

N = N₀ × 0.5^n

where, N is the remaining mass, N₀ is the original mass, and n is the number of half lives.

Therefore;

n = time ÷ half life

   = 32 days ÷ 8 days

  = 4

Therefore;

Remaining mass = 40.0 mg × 0.5^4

                            = 2.5 mg

Hence, the remaining mass of I-131 after 32 days is 2.5 mg