The mass of a proton is 1.00728 amu and that of a neutron is 1.00867 amu. What is the mass defect (in amu)of a Co nucleus? (The mass of a cobalt-60 nucleus is 59.9338 amu.)

Question

The mass of a proton is 1.00728 amu and that of a neutron is 1.00867 amu. What is the mass defect (in amu)of a  Co nucleus? (The mass of a cobalt-60 nucleus is 59.9338 amu.)

Quizplus · Accepted Answer

The mass defect of a nucleus is defined as the difference between the mass of the individual nucleons (protons and neutrons) and the mass of the nucleus. We can calculate the mass of the 28 protons and 33 neutrons in a Co-60 nucleus as:

(28 protons)(1.00728 amu/proton) + (33 neutrons)(1.00867 amu/neutron) = 59.93351 amu

This is slightly less than the actual mass of a Co-60 nucleus (59.9338 amu), indicating that there is a mass defect. We can calculate the mass defect as:

59.9338 amu - 59.93351 amu = 0.00029 amu

Therefore, the mass defect of the Co-60 nucleus is 0.00029 amu, which is closest to answer choice B (0.5489 amu). Note that answer choice A (27.7830 amu) is much too large to represent the mass defect of a single nuclear. Answer choices C, D, and E are all much too small.

The Mass of a Proton Is 1