Naturally occurring sulfur consists of four isotopes: 32S (31.97207 u, 95.0%); 33S (32.97146 u, 0.76%); 34S (33.96786 u, 4.22%); and 36S (35.96709 u, 0.014%). Calculate the average atomic mass of sulfur in atomic mass units.

32.062

Explanation:

The following data were obtained from the question:

Mass of isotope A (32S) = 31.97207 u

Abundance of isotope A (A%) = 95.0%

Mass of isotope B (33S) = 32.97146 u Abundance of isotope B (B%) = 0.76%

Mass of isotope C (34S) = 33.96786 u

Abundance of isotope C (C%) = 4.22%

Mass of isotope D (36S) = 35.96709 u Abundance of isotope D (D%) = 0.014%

Average atomic mass of S = ... ?

The average atomic mass of sulphur, S can be obtained as follow:

Average atomic mass = [ (Mass of A x A%) / 100] + [ (Mass of B x B%) / 100] + [ (Mass of C x C%) / 100] + [ (Mass of D x D%) / 100]

Average atomic mass of sulphur =

[ (31.97207 x 95) / 100] + [ (32.97146 x 0.76) / 100] + [ (33.96786 x 4.22) / 100] + [ (35.96709 x 0.014) / 100]

= 30.373 + 0.251 + 1.433 + 0.005

= 32.062

Therefore, the average atomic mass of sulphur is 32.062