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#