Chemistry Isotopes Solution: An unknown element with atomic weight 125.8 amu ha...

Solution: An unknown element with atomic weight 125.8 amu has two isotopes. One isotope has an abundance of 51.97% at 125.6 amu. Find the mass of the second isotope.A. 126 B. 100 C. 148 D. 531 E. Over 9000

Problem

An unknown element with atomic weight 125.8 amu has two isotopes. One isotope has an abundance of 51.97% at 125.6 amu. Find the mass of the second isotope.

A. 126 

B. 100 

C. 148 

D. 531 

E. Over 9000

Solution

Determine the mass of the second isotope of an unknown element with a weight of 125.8 amu where the other isotope has 51.97% at 125.6 amu using the formula for atomic mass

atomic mass = mass × f.a. isotope 1 +mass × f.a. isotope 2


where atomic mass = average atomic mass of the element and f.a. = fractional abundance of the isotope. To get f.a., we simply need to divide the given percent abundance by 100.


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