A 3.60 g sample of radium-226 (atomic mass = 226 g mol ) has an initial activity of…

CHEMISTRY · Multi-part · US High School · Chemistry · Atomic Structure & Nuclear · Atomic Structure & Nuclear

Problem

A 3.60 g sample of radium-226 (atomic mass = 226 g mol−1^{-1}) has an initial activity of 1.00×10111.00 \times 10^{11} decays s−1^{-1}. (Use NA=6.022×1023 mol−1N_A = 6.022 \times 10^{23}\,\text{mol}^{-1}.) (i) Determine the decay constant of radium-226. (ii) Calculate the half-life of radium-226 in years. (iii) After how many years will the activity fall to 2.50×10102.50 \times 10^{10} decays s−1^{-1}?

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