Strontium-90 is radioactive and has a half life of 28.8 years. How much of a 2.20mg sample would be left after 117. years?Round your answer to 2 significant digits. Also, be sure your answer has a unit symbol.
Question
Strontium-90 is radioactive and has a half life of 28.8 years. How much of a 2.20mg sample would be left after 117. years?Round your answer to 2 significant digits. Also, be sure your answer has a unit symbol.
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 T is the half-life of the substance
Given: N0 = 2.20 mg t = 117 years T = 28.8 years
Substituting these values into the formula, we get:
N = 2.20 mg * (1/2)^(117/28.8)
Calculating the exponent first:
117/28.8 = 4.06
So, the equation becomes:
N = 2.20 mg * (1/2)^4.06
Calculating the second part:
(1/2)^4.06 = 0.060
So, the equation becomes:
N = 2.20 mg * 0.060
Finally, multiplying these values together gives:
N = 0.132 mg
Rounding to two significant digits, we get:
N = 0.13 mg
So, after 117 years, 0.13 mg of the Strontium-90 sample would be left.
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