Question

1. Calculate the binding energy (kJ/mol) for ⁸⁴Kr.

¹H = 1.00785 g/mol, ¹n = 1.008665 g/mol, ⁸⁴Kr = 83.91151 g/mol

2. Predict the mode of radioactive decay for ²²⁹Ac.

A)	alpha-decay

B)	beta-decay

C)	positron emission

D)	neutron emission

E)	proton emission

Answer 1

Q1) Mass defect of 84 Kr is

      = [at. no. x mass of H + no. of nuetronsx mass of neutrons] - mass of Kr

     = [36x 1.00785 + 48 x 1.008665] - 83.91151 = 0.78701 amu

the binding energy = mass defect x 931.478 MeV = mass defect x 931,478 x 1.602 x 10^-13J

                            = 0.78701 x 931.478 x 1.602 x 10^-13 J

                           = 1174.398 x 10^-13J = 1.174 x10^-10 J

Q2) Most of the elements with mass numbers greater than 200 have n/p ratio greater than the stable ratio, thus can undergo alpha emission which is usually followed by beta emission.

   Here Actinium the common isotope has atomic mass 227, the given isotope has 229 as its mass, thus it decays by beta emission.