A scientist wishes to find the age of a sample of rock. Realising that it contains radioactive potassium, which decays to give a stable form of argon, the scientist started by making the following measurments:(adsbygoogle = window.adsbygoogle || []).push({});

decay rate of the potassium in the sample = 0.16Bq

mass of potassium in the sample = 0.6x10^-6g

mass of argon in the sample = 4.2x10^-6g

The Molar mass of the potassium is 40g. show that the decay constant for potassium is 1.8x10-17 and its half-life is 1.2x10^9years.

2. Relevant equations

decay constant = a/N

n=m/Mr

3. The attempt at a solution

N=m/Mr

N=0.6x10^-6/40

N=1.5x10^-8

N=1.5x10^-8 x 6.02x10^-8

N=9.03 x 10^-16

decay constant = a/N

decay constant = 0.16/9.03x10^-16

I got this far then got stck as the answer was wrong, im not sure wher to go from here any help would be appreciated.

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# Homework Help: Calculating decay constants and half-life

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