Question

4. An analysis of a mineral in Rock Sample B-273 reveals that only 6.25% of the original parent radionuclide carbon-14 remains. A) What is the stable daughter isotope we would also find? B) How many half-lives have elapsed in Rock Sample B-2737 C) How old is Rock Sample B-273? Be sure to show your work. 5. An analysis of a mineral in Rock Sample C-451 reveals that 75% of the original parent radionuclide uranium-238 remains. A) What is the stable daughter isotope we would also find? d os senosni obilno B) How many half-lives have elapsed in Rock Sample C-4517 C) How old is Rock Sample C-4517 Be sure to show your work. 6 Why is it improbable that scientists will discover a terrestrial rock containing minerals with an original parent isotope of rubidium-87 where 2 half-lives have elapsed?

Answer 1

Q4 as question suggest that rock sample has carbon left so initially it would have Carbon only and it would be converting to stable isotope by radioactivity.

A)And by table we see that stable daughter isotope of Carbon is Nitrogen -14.

B) 6.25% of original parent nucleide is left so

After 1half yr , radioactive nuclie left is 50% of original.

After 2half yr , radioactive nuclei left is 25% of orginal (50-50/2)

After 3 half yr, radioactive nuclei left is 12.5% of original( 25-25/2)

After 4 half yr, radioactive nuclei left is 6.25% of original ( 12.5-12.5/2)

So 4 half yrs are done to obtain such sample which contains 6.25% of original parent nucleide.

C) to find how old the rock sample is equal to time spent in all life yrs = 4*time of 1halfyr = 4*(5.73*10^3) = 22.92*10^3 yrs