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A radioactive element has an initial count rate of 2,400 counts per minute on a scaler. The count rate falls to 300 units per minute...

A radioactive element has an initial count rate of 2,400 counts per minute on a scaler. The count rate falls to 300 units per minute in 30 hours, (a) Calculate the half-life of the element (b) If the initial number of atoms in another sample of the same element is 6.0 × 1020, how many atoms will have decayed in 50 hours?

Answers

Mutiso
a) 2,400 × ½ × ½ × ½ = 300
Three half-lives have a total of 30 hours, thus half-life = 30 /3 = 10 hours
b) Since half-life = 10 hrs half-lives in 50 hrs = 50/10 = 5 hrs.
So the remaining undecayed atoms are ½ × ½ × ½ × ½ × ½ × 6.0 × 1020
= 0.1875 × 1020, thus
The number of atoms which have decayed = (6.0 – 0.1875) × 1020
= 5.812 × 1020
Mutiso answered the question on October 17, 2018 at 10:14

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