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A radioactive isotope has initial activi...

A radioactive isotope has initial activity of `28` dpm Its activity is reduced to `14` dpm after half an hour. The initial number of nuclide in sample was:

A

200

B

400

C

600

D

1200

Text Solution

Verified by Experts

The correct Answer is:
D
`lambda=(2.303)/(t) "log"(N_(0))/(N)`
`(N_(0))/(N)=(28)/(14)=2, t=(1)/(2)` hours=30 min
`lambda=(2.303)/(30 "min") "log"2`
`=(2.303xx0.3010)/(30) "min"^(-1)`
`=0.0231 "min"^(-1)`
Rate `=lambda N_(0)`
`28=0.0231xxN_(0)`
`N_(0)=(28)/(0.0231)=1212~~1200`
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