Question

The mass of a lithium?7 atom is 7.016003 amu. What is the nuclear binding energy of a lithium?7 nucleus in units of kJ/mol and eV/nucleus? Enter your answers in scientific notation.

Answer 1

Given that mass of a lithium?7 atom is 7.016003 amu

mass of Li-7 = 7.016003 amu
number of protons = 3
mass of protons in Li = 3 * 1.007825 = 3.023475
mass of neutrons = (4*1.008665) = 4.03466
total mass of nucleons = 3.023475+4.03466=7.058135
mass defect (dm)= 7.058135 - 7.016003 = 0.042132

B.E. = dM * c^2

C = velocity of light

B.E.= 0.042132 amu * 1.660*10^-27 kg / 1 amu (3.0*10^8 m/s)^2

= 6.2945*10^-12 kg m^2/c^2 *1 J /1 kg m^2/s^2 *1 kg/ 10^3 J

= 6.29*10^-15 KJ *6.03*10^23 mole^-1

= 3.79*10^9 KJ/ mole

And binding per nucleaon = total energy / number of nucleon

= 0.042132 amu *931.5*10^6 eV/1 amu

= 3.924*10^7 eV / nucleon