The half life for the radioactive decay of rubidium-87 to strontium-87 is ×4.881010 years.Suppose nuclear chemical analysis shows that there is 0.799mmol of strontium-87 for every 1.000mmol of rubidium-87 in a certain sample of rock. Calculate the age of the rock.Round your answer to 2 significant digits.
Question
The half life for the radioactive decay of rubidium-87 to strontium-87 is ×4.881010 years.Suppose nuclear chemical analysis shows that there is 0.799mmol of strontium-87 for every 1.000mmol of rubidium-87 in a certain sample of rock. Calculate the age of the rock.Round your answer to 2 significant digits.
Solution
To solve this problem, we need to use the formula for radioactive decay, which is:
N = N0 * (1/2)^(t/T)
where: N is the final quantity of the substance, N0 is the initial quantity of the substance, t is the time that has passed, and T is the half-life of the substance.
In this case, we know that the ratio of strontium-87 to rubidium-87 is 0.799, so we can say that N/N0 = 0.799.
We also know that the half-life T of rubidium-87 is 4.88 billion years.
Substituting these values into the formula, we get:
0.799 = (1/2)^(t/4.88)
To solve for t, we can take the natural logarithm of both sides:
ln(0.799) = (t/4.88) * ln(1/2)
Solving for t gives:
t = 4.88 * (ln(0.799) / ln(1/2))
Calculating this gives:
t ≈ 6.43 billion years
So, the age of the rock is approximately 6.43 billion years, rounded to two significant digits.
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