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A 320.9 ng sample of an unknown radioactive substance was placed in storage and its mass measured periodically. After 47 days the amount of radioactive substance had decreased to 40.11 ng. How many half‑lives of the unknown radioactive substance have occurred?

Respuesta :

Answer:

3 half life of the unknown radioactive substance have occurred.

Explanation:

Mass of sample = 320.9 ng

Mass after 1 half life = 0.5 x 320.9 = 160.45 ng

Mass after 2 half life = 0.5 x 160.45 = 80.225 ng

Mass after 3 half life = 0.5 x 80.225 =40.11 ng

So 3 half life of the unknown radioactive substance have occurred.