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Radon-222 has a half-life of 3.8 days. I...

Radon-222 has a half-life of 3.8 days. If one starts with 0.064 kg of Radon-222 the quantity of Radon-222 left after 19 days will be -

(A) 0.002 kg.
(B) 0.062 kg.
(C) 0.032 kg.
(D) 0.024 kg.

A

0.002 kg

B

0.062 kg

C

0.032 kg

D

0.024 kg

Text Solution

Verified by Experts

The correct Answer is:
A
Given : For Radon-222,
Half life `= T_(1//2)` = 3.8 days, time = t = 19 days.
`therefore` Number of half lives in time t, n `= (9)/(3.8) = 5`
The remaining quantity of Radon-222 after 5 half lives,
`N = ((1)/(2))^(5)N_(0)" "(because N_(0) = 0.064 kg)`
`= ((1)/(2))^(5) xx 0.064 kg= 0.002 kg`
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