Question

Bromine's two major isotopes are bromine-79 and bromine-81. The average atomic mass for bromine on the periodic table is 79.904 amu. Given this information, what can you conclude about the percent composition of the isotopes in nature?

Answer 1

Bromine-79 = 55%

Bromine-81 = 45%

Step-by-step explanation:

Take y as the percentage of 79, this means the percentage of 81 would be 100 - the percentage of 79 (y).

((79 x y) + (81 x (100 - y)) ÷ 100 = 79.904

(79 x y) + (81 x (100 - y) = 7990.4

79y + 8100 - 81y = 7990.4

-2y + 8100 = 7990.4

-2y = -110

y = 55

Bromine-79 = 55%

Bromine-81 = 100 - 55 = 45%