A medical laboratory stores of iodine-131 (half-life ) for diagnostic use

PHYSICS · Multi-part · A Level · Physics · Nuclear physics · Nuclear physics

Problem

A medical laboratory stores

2.0\,\text{g}

of iodine-131 (half-life

8.0\,\text{d}

) for diagnostic use. (Given: molar mass of iodine-131

=131\,\text{g\,mol}^{-1}

, Avogadro constant

N_A=6.02\times10^{23}\,\text{mol}^{-1}

.) (i) Calculate the initial number of iodine-131 nuclei in the store. (ii) After

40\,\text{d}

, determine the mass of iodine-131 still remaining. (iii) Find the total number of nuclei that have decayed during these

40\,\text{d}

and express this number as a percentage of the initial nuclei.