A sample of the radioactive nuclide Pt is prepared That has an initial activity

Question

A sample of the radioactive nuclide Pt is prepared That has an initial activity of 7.54 times 10^11 Bq : 92.4 min after the sample is prepared, tha activity has fallen to 9.45 times10^10 Bq. What is the half-life of this nuclide? N = N_0 e^-xt -lamada t = ln(0.12533) lamada = 0.02247 t_1/2 = 0.693/0.0224 9.45 times 10^10 Bq = (7.54 times 10^10 Bq)e^-xt 9.45 times 10^10 Bq/9.45 times 10^11 Bq = e^-lamada t Part B: How many radioactive nulcei were initially present in the sample? radioactive nuclei

Explanation / Answer

Solution:

1 Bequeral = 1 disintegration / s

Disintegration constant = 0.693/(30.8*60s) = 0.000375 /s

No. of nuclei = no. of moles x Avogadro number = Rate of disintegration / decay constant

                                                                             = ( 7.54 x 1011 ) / (0.000375)

                                                                              = 2.0 x 1015

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