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# During nuclear explosion, one of the products is 90Sr with half-life of 28.1 years. If 1μg of 90Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically. - CBSE (Science) Class 12 - Chemistry

ConceptIntegrated Rate Equations Half-life of a Reaction

#### Question

During nuclear explosion, one of the products is 90Sr with half-life of 28.1 years. If 1μg of 90Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically.

#### Solution

Here, k = 0.693/t_"1/2" = 0.693/28.1 y^(-1)

It is known that,

t = 2.303/k log  ([R]_0)/([R])

=> 10 = 2.303/(0.693/28.1) log  1/[R]

=>10 = 2.303/(0693/28.1)(-log [R])

=> log [R] = -(10xx0.693)/(2.303xx28.1)

=>[R] = antilog (-0.1071)

= antilog((bar"1".8929)

= 0.7814 mug

Therefore, 0.7814 μg of 90Sr will remain after 10 years.

Again,

 t= 2.303/k log  ([R]_0)/([R])

=> 60 = 2.303/(0.693/28.1) log  1/[R]

=>log[R] = -(60xx0.693)/(2.303xx28.1)

=>[R] = antilog (-0.6425)

=antilog(bar"1".3575)

= 0.2278 mug

Therefore, 0.2278 μg of 90Sr will remain after 60 years

Is there an error in this question or solution?

#### APPEARS IN

NCERT Solution for Chemistry Textbook for Class 12 (2018 to Current)
Chapter 4: Chemical Kinetics
Q: 17 | Page no. 119

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Solution During nuclear explosion, one of the products is 90Sr with half-life of 28.1 years. If 1μg of 90Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically. Concept: Integrated Rate Equations - Half-life of a Reaction.
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