35. (a) We assume that the chlorine in the sample had the naturally occurring isotopic mixture, so the average mass number was 35.453, as given in Appendix F. Then, the mass of 226Ra was m=+=×−226226 2 35010761 103.453..afgg.The mass of a 226Ra nucleus is (226 u)(1.661 ×10– 24g/u) = 3.75 ×10– 22g, so the number of 226Ra nuclei present was N= (76.1 ×10– 3
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