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: 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.
Your method is correct, you must just be punching the numbers into your calculator wrong. How many K atoms did you calculate?
As I said above, your method was spot on but you were probably just hitting the wrong buttons on your calculator.