Iridium-192 is one radioisotope used in brachytherapy in which a radioactive source is placed inside a patient's body to treat cancer. brachytherapy allows the use of a higher than normal dose to be placed near the tumor while lowering the risk of damage to healthy tissue. iridium-192 is often used in the head or breast. if a sample of iridium-192 is initially 3.25g and 1.21g remains after 105 days, estimate the half-life of the radioisotope.

Question

Reginald Daniel

Chemistry

3 September, 21:51

Iridium-192 is one radioisotope used in brachytherapy in which a radioactive source is placed inside a patient's body to treat cancer. brachytherapy allows the use of a higher than normal dose to be placed near the tumor while lowering the risk of damage to healthy tissue. iridium-192 is often used in the head or breast. if a sample of iridium-192 is initially 3.25g and 1.21g remains after 105 days, estimate the half-life of the radioisotope.

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Paul Boyd · Answer 1

Answer is: the half-life of the radioisotope is 74 days.

m₀ = 3.25 g.

m₁ = 1.21 g.

t = 105 d.

ln (m₀/m₁) = k· t.

ln (3.25/1.21) = k·105 d.

ln (2.685) = 105·k.

0.98 = 105k.

k = 0.0094.

t1/2 = ln2 / k.

t1/2 = 0.693 / 0.0094.

t1/2 = 73.72 days.