1.

10 g of a radioactive isotope is reduced to 1.25 g in 12 years. Therefore, half-life period of the isotope is

Answer»

24 years
4 years
3 years
8 years

Solution :(b) : `[A]=([A]_(0))/(2^(n)):.1.25=(10)/(2^(n))" or "2^(n)=(10)/(1.25)=8=2^(3):.n=3`
i.e., 3 half LIVES = 12 yrs. `" or "t_(1//2)=4" yr"`
ALTERNATIVELY, `10goverset(t_(1//2))to5goverset(t_(1//2))to2.5goverset(t_(1//2))to1.25g`
`3xxt_(1//2)=12" yror"t_(1//2)=4" yr".`


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