1.

The half-life of Rn is 46 days, what amount will be left from 2 mole of it after 138 days?

Answer»

`0.25` mole
`1.25` mole
`0.40` mole
`0.62` mole

Solution :Number of half lives gone = `(138)/(46) = 3`
`N_0 = 2` mole, `N_t = ?`
As, `N_t = N_0 xx (1/2)^(n) implies N_t= 2 xx (1/2)^(3) = 2/8 = 0.25` mole.
HENCE 0.25 mole of .Rn. will be LEFT from 2 mole of it after 138 days.


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