5. After undergoing 4 half-lifes what % of a 150 g sample of I-L-L will remain?

6.25%

Explanation:

Given data:

Total sample = 150 g

Percentage remain after 4 half life = ?

Solution:

at time zero 150 g

At first half life = 150 g/2 = 75 g

At 2nd half life = 75 g/ 2 = 37.5 g

At 3rd half life = 37.5 g/2 = 18.75 g

At 3rd half life = 18.75 g/2 = 9.375 g

Percentage remain after 4 half lives.

9.375 g / 150 g × 100

0.0625 × 100

6.25%

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