Indium (in) is made up of 95.7% 115in and 4.3% 113in. the atomic mass of 113in is 112.904 amu. the atomic mass of 115in is 114.904 amu. what is the average atomic mass of a sample of indium?

amu In = 114.818 amu

Explanation:

Indium (In):

∴ 95.7% 115In

∴ 4.3% 113In

∴ atomic mass 113In = 112.904 amu

∴ atomic mass 115In = 114.904 amu

average atomic mass (In):

⇒ amu In = (0.957)(114.904 amu) + (0.043)(112.902 amu)

⇒ amu In = 109.963 amu + 4.855 amu

⇒ amu In = 114.818 amu

the answer is d. 74.02