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sp2606 [1]
3 years ago
10

A rock outcrop was found to have 95.82% of its parent U- 238 isotope remaining. Approximate the age of the outcrop. The half-lif

e of U- 238 is 4.5 billion years old.
A) 277 million years

B) 1.7 billion years

C) 14 million years

D) 21 million years
Mathematics
1 answer:
mixer [17]3 years ago
5 0

Answer:

A) 277 million years

Step-by-step explanation:

Here, decay of U-238 is first order reaction. (since most of the nuclear decays are first order).

so, the equation t = \frac{1}{k} × ln(\frac{A(0)}{A})

where, t = time from start of reaction

           k = reaction constant

           A(0) = initial concentration; A = present concentration.

     ⇒ 4.5 billion = 4500 million years = \frac{1}{k}× ln2.

Now, given 95.82% of parent U-238 isotope is left.

⇒ t = \frac{1}{k} × ln(\frac{A(0)}{A})

  t = \frac{4500}{ln2} × ln(\frac{100}{95.82})

⇒ t ≅ 277 million years.

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