Question

A hypothetical element has two main isotopes. One has a mass of 54 amu and the other has a mass of 56 amu. If the atomic weight of this element is 54.37 amu, what is the percent abundance of the 56 amu isotope?
A) 1. 78.52%
B) 2. 81.52%
C) 3. 75.52%
D) 4. 18.48%
E) 5. 21.48%

Answer 1

Answer:

The answer to your question is: letter D

Explanation:

Data

Isotope mass 1 = 54 amu

Isotope mass 2 = 56 amu

Atomic weight = 54.37 amu

Percent abundance of isotope 2 = ? = X

Percent abundance of isotope 1 = 1 - x

Formula

Atomic weight = (Mass isotope 1)(1 - x) + (mass isotope 2)(x)

Process

Place the data in the formula and solve for x.

54.37 = 54( 1 - x) + 56x

54.37 = 54 - 54x + 56x

54.37 - 54 = -54x + 56x

0.37 = 2x

x = 0.37 / 2

x = 0.185

To find the percent multiply by 100

x = 0.185 x 100

x = 18.5 % = Mass of isotope 2

Mass of isotope 1 = 100 - 18.5 = 81.5 %