Question

Germanium has 5 isotopes. The average atomic mass from the periodic table is 72.63.

A)Find the missing abundance.
B) Use the atomic mass to calculate the mass of the missing isotope.

Answer 1

75.92

Step-by-step explanation:

A)the % abundance adds up to 100, so adding all the % abundances of Ge:

20.52 + 27.45 + 7.76 + 36.52 = 92.25

The remaining % abundance is:

100 - 92.25 = 7.75%

B) Using this formula:

`atomic \: mass = (sum \: of \: (\% \: isotope \: abundance * isotope \: mass))/(100)`

`72.63 = ((20.52 * 69.92) + (27.45 * 71.93) + (7.76 * 72.92) + (36.52 * 73.92) + (7.75x))/(100)`

multiply both sides by 100 to get rid of the fraction:

`7263= {(20.52 * 69.92) + (27.45 * 71.93) + (7.76 * 72.92) + (36.52 * 73.92) + (7.75x)}{}`

multiplying each bracket:

`7263 = 1434.7584 + 1974.4785 + 565.8592 + 2699.5584 + 7.75x`

adding up the terms:

`7263 = 6674.6545 + 7.75x`

subtract 6674.6545 on both sides to give:

`588.3455 = 7.75x`

divide both sides by 7.75:

`x = (588.3455)/(7.75) = 75.92 \: (2dp)`