Posted by Joe on .
I need to find the average molar mass of an unknown element. The atomic mass is 120; the mass numbers of isotopes are 295, 296, 297, 298 and 299; the percent of each isotope is 2.356%, 4.325%, 15.652%, 48.452% and 29.215%. The mass of the neutron is 1.67262164x10^-24g and the mass of a proton is 1.67492721x10^-24g. The mass defect is 0.76132613%.
mass proton x 120 = ?p
mass neutron x (29?-120) = ?n
total mass = ?p+?n x %mass def/100 = ?mass isotope.
(mass isotope x %/100) + (mass isotope x %/100) ........etc for all the isotopes. The total is the average atomic mass.