Sodium-24 has a half-life of 15.0 hours. Suppose you had a sample containing 0.010 moles of Na-24. How many hours would be required to reduce your sample to 6.25 x 10^-4 moles?

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Answer 1 · 2016-05-24T06:41:08

$time = 60.0 \ hrs$

$n_i=n_r*2^n$

$n_i " is the initial number of moles present of the radioisotope."$

$n_r" is the number of moles remaining after a certain time "$

$n " is the number of periods," = (time)/T" where T is the half-life."$

$n_i=n_r*2^n$

$n_i/n_r=2^n$

$2^n=(0.010\ mol)/(6.25xx10^(-4)\ mol)$

$2^n=16$

$2^n=2^4$

$(n=4)$

$n= (time)/T"$

$time= nxx T " (half-life)"$

$time = 4xx15.0 hrs$

$time = 60.0 \ hrs$