A certain element contains eleven atoms of mass 95.952 u for every four atoms of mass 98.949 u. Compute the average atomic weight of this element.
A) 97.451 u
B) 96.754 u
C) 98.150 u
D) 105.16 u
E) 96.952 u

Question

Quizplus · Accepted Answer

To calculate the average atomic weight of the element, we need to consider the relative abundance of each isotope of the element.

Let x be the abundance of the isotope with mass 95.952 u, and y be the abundance of the isotope with mass 98.949 u.

We are given that there are 11 atoms of the first isotope for every 4 atoms of the second isotope.

So we can write:

x/y = 11/4

or

x = 11y/4

We also know that the atomic weight (mass) of the element is a weighted average of the mass of the two isotopes:

Average atomic weight = (x*95.952 + y*98.949)/(x+y)

Substituting x = 11y/4, we get:

Average atomic weight = (11y/4*95.952 + y*98.949)/(11y/4+y)

Simplifying, we get:

Average atomic weight = 96.754 u

Therefore, the answer is B.

A Certain Element Contains Eleven Atoms of Mass 95