Question

An element has two naturally-occurring isotopes. The mass numbers of these isotopes are 111 amu and 113 amu, with natural abundances of 75% and 25%, respectively. Calculate its average atomic mass.

Answer 1

Average Atomic Mass=111.5amu

- massno of Iso toße) Average Atornic (%o natural Aboundance mass - 100 Isotope A mass no. = m = H0 111 amy S olo natural aboundance = G = 751. Isotope B mass no am₂ = 113 smy / noperal aboundance= C₂ =251. (m,x4) + (mix C22 Average atomic mass 780 (1+1, x 75) + (113*25) = Average Atomic = 111.5 amu. mass = 111.5 amy]