1.

During nuclear explosion, one of the products is ""^(90)"Sr" with half life of 28.1 years. If 1 mug of ""^(90)"Sr" was absorbed in 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 ?

Answer»

Solution :As radioactive disintegrations follow first order kinetics,
Decay CONSTANT of `""^(90)"Sr "(k)=(0.693)/(t_(1//2))=(0.693)/(28.1" y")=2.466xx10^(-2)y^(-1)`
To CALCULATE the amount left after 10 years.
`a=1 mug,t=10" years,"k=2.466xx10^(-2)y^(-1),(a-x)=?`
`k=(2.303)/(t)log""(a)/(a-x)`
`2.466xx10^(-2)=(2.303)/(10)log""(1)/((a-x))" or "log(a-x)=-0.1071`
or `(a-x)=" Antilog "=1.8929=0.7814 mug`
To Calculate the amount left after 60 years.
`2.466xx10^(-2)=(2.303)/(60)log""(1)/(a-x)" or "log(a-x)=-0.6425`
or `(a-x)=" Antilog T"*3575=0.2278" "mug.`


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