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The half-life of radioactive sodium is 1...

The half-life of radioactive sodium is 15.0 hours. How many hours would it taken for 64 gms of sodium to decay one-eighth of its original value

A

3

B

15

C

30

D

45

Text Solution

Verified by Experts

The correct Answer is:
D
`because 2.303 "log" (N_0)/(N) = lambda t " "…..(i)`
and `lambda = (0.693)/(t_(1//2)) = (0.693)/(15)`
or `lambda = 0.0462`
`therefore` using equation (i) we get
2.303 log `(64)/(8) = 0.0462 xx t `
or t = 45 hr.
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