Calculate the mass defect in Ni-59 if the mass of a Ni-59 nucleus is 58.69344 amu.The mass of a proton is 1.00728 amu and the mass of a neutron is 1.008665 amu.

Question

Quizplus · Accepted Answer

The mass of Ni-59 nucleus = 58.69344 amu
Number of protons in Ni-59 = 28 (as the atomic number of Nickel is 28)
Number of neutrons in Ni-59 = 59 - 28 = 31

Total mass of 28 protons = 28 x 1.00728 amu = 28.2 amu
Total mass of 31 neutrons = 31 x 1.008665 amu = 31.3 amu
Therefore, total mass of protons and neutrons = 28.2 + 31.3 = 59.5 amu

Mass defect = (actual mass - total mass of protons and neutrons)
= 58.69344 amu - 59.5 amu
= -0.80656 amu
(Note that the mass defect is negative because the actual mass is less than the total mass of protons and neutrons)

Therefore, the mass defect in Ni-59 = 0.80656 amu

However, the question asks for the mass defect in terms of difference between neutron and proton masses.

Mass of a neutron = 1.008665 amu
Mass of a proton = 1.00728 amu
Mass excess of a neutron = 0.78234 amu (mass of a neutron - mass of a proton)

Mass defect = (number of protons x mass excess of a proton) + (number of neutrons x mass excess of a neutron)
= (28 x 0.78234) + (31 x 0.008315)
= 21.88792 + 0.25797
=0.77902 amu

Therefore, the best answer is B, which is 0.77902 amu.

Calculate the Mass Defect in Ni-59 If the Mass of a Ni-59