The half-life of Palladium-100 is 4 days. After 24 days a sample of Palladium-100 has been reduced to a mass of 5 mg. What was the initial mass (in mg) of the sample?

Question

What is the mass 7 weeks after the start?

Answer 1

Equation for half-life:

Final amount = initial amount x (1/2) ^ (total time/half-life)

So,

5 = Initial amount x (1/2) ^ (24/4)

5 = Initial amount x (1/2) ^ (6)

5= Initial amount x (1/64)

5 * 64 = initial amount x (1/64) x 64

320 = initial amount.

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After 7 weeks,

Final amount = 320 x (1/2) ^ (49 days / 4 days)

Final amount = 0.07