Nuclear and Organic Chemistry

In a theoretical procedure, one-half of the uncharged nucleons in a chlorine-35 atom are isolated and weighed. Noting that the mass of a proton is 1.672 × 10-27 kg while that of a neutron is 1.675 × 10-27 kg, the total mass of this collected sample will be closest to: A. 2.5 × 10-25 kg. This answer is not correct. B. 6.0 × 10-25 kg. This answer is not correct. C. 1.5 × 10^-26 kg. C is correct. For our purposes, we can treat protons and neutrons as though they have the same mass. However, this question references “uncharged nucleons,” meaning neutrons. One 35Cl atom contains 18 neutrons, so half of that number gives us 9. Since the mass of one neutron is 1.67 × 10^-27 kg, we can multiply by 9 to get 1.5 × 10^-26 kg. D. 3.0 × 10-26 kg. This is the mass of all 18 neutrons rather than half of them.