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)96.751 u
C)98.150 u
D)105.16 u
E)96.952 u

Question

Quizplus · Accepted Answer

We can use the formula for calculating the average atomic weight:

average atomic weight = (fractional abundance of isotope A)(mass of isotope A) + (fractional abundance of isotope B)(mass of isotope B) + ...

Let x be the fractional abundance of the first isotope (mass 95.952 u). Then the fractional abundance of the second isotope (mass 98.949 u) is 4x (since there are 4 atoms of the second isotope for every 11 atoms of the first isotope).

We can set up the equation:

x(95.952 u) + 4x(98.949 u) = average atomic weight

Simplifying and solving for x, we get:

x = 0.2199

Substituting back into the equation, we get the average atomic weight:

average atomic weight = (0.2199)(95.952 u) + (0.8796)(98.949 u) = 96.751 u

A Certain Element Contains Eleven Atoms of Mass 95