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A small amount of solution containing \mathrm{Na}^{24} ruclides with activity 20,500 disintegration per second was injected in the blood stream of a person - The activity of 1 \mathrm{ml} of blood sample taken after 5 hour later. was found to be 20 aisintegration / \mathrm{min} \cdot t_{1 / 2}=15 hours. total volume of blood of the person is:

Option: 1

40 \text { ltr }


Option: 2

36 \text { ltr }


Option: 3

45 \text { ltr }


Option: 4

49 \text { ltr }


Answers (1)

best_answer

Let volume of blood of person is V. 

\mathrm{Na}^{24} is uniformly mixed in V volume of blood.
Activity of \mathrm{Na}^{24} & total no. of nuclei

 A_0= Activity of \mathrm{Na}^{24} of 1 ml sample

=\frac{20500}{\mathrm{Vme}} \times 1 \mathrm{ml}=\frac{20500}{\mathrm{~V}}
Activity after  5 \, \mathrm{hrs}=\mathrm{Ao} / \mathrm{2}^{\mathrm{n}}.

n=\frac{t}{t^{1} / 2}=\frac{5}{15}=1 / 3 . \quad \Rightarrow A=A_0 / 2^{1 / 3}

\Rightarrow \frac{20}{60}=\frac{A_0}{2^{1 / 3}} \Rightarrow A=2^{1 / 3} / 3

\Rightarrow \frac{20500}{v}=\frac{2^{1 / 3}}{3} \Rightarrow v=\frac{20500 \times 3}{2^{1} / 3} \mathrm{ml}

v=48.8\, \, ltr\, \, =49\, ltr .

Posted by

Kuldeep Maurya

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