Question

if the abundance of 1st isotope is 49.7%.while the 2nd one is 50.3%. calculate the average atomic mass of bromine?

Answer 1

according to me its 45.5

Answer 2

Formula to calculate average atomic weight :

(exact weight of isotope #1) (abundance of isotope #1) + (exact weight of isotope #2) (abundance of isotope #2)/100 = average atomic weight of the element.

Br 79 = atomic wt 79 , % abundance 49.7

Br 81 = atomic wt. 81, % abundance 50.3

Putting the values in above formula we get Average atomic mass of Br =

(79 x 49.7) + (81 x 50.3) / 100

(3926.3 + 4074.3) / 100 = 80.036 grams