Question

The ages of rocks that contain fossils can be determined using the isotope 87Rb. This isotope of rubidium undergoes beta

Answer 1

Answer:

Age of rock = 722 million years old

Explanation:

Using the formula; fraction remaining = 0.5ⁿ

where n = number of half lives elapsed.

However, from the given values, fraction remaining = 1.000 - 0.0105

fraction remaining = 0.9895

Substituting in the formula to determine the number of half-lives:

0.9895 = 0.5ⁿ

log 0.9895 = n log 0.5  

-0.0045842 = -0.30103 n

number of half lives elapsed, n = 0.0152

Therefore age of rock = 0.0152 x 4.75 x 10¹⁰ years =  7.22 x10⁸ years

Age of rock = 722 million years old