A laboratory has a sealed source containing of

PHYSICS · Multi-part · CBSE · Physics · Nuclei · Nuclei

Problem

A laboratory has a sealed source containing 2.0 g2.0\,\text{g} of 226 ⁣Ra^{226}\!\mathrm{Ra}, whose half-life is 1.6×103 yr1.6\times10^{3}\,\text{yr}. (Atomic mass of radium =226 g mol−1=226\,\text{g mol}^{-1}; NA=6.02×1023 mol−1N_A = 6.02\times10^{23}\,\text{mol}^{-1}.) (i) Calculate the activity of the source at the present moment, expressing your answer in becquerel. (ii) Find the activity of the same source after 5.0 yr5.0\,\text{yr}. (iii) Determine the percentage decrease in activity that occurs in this 5.0 yr5.0\,\text{yr} interval.

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