Q2.5CYL - Chemistry (OpenStax)

Question

_{Naturally occurring copper consists of 63Cu (mass 62.9296 amu) and 65Cu (mass 64.9278 amu), with an average mass of 63.546 amu. What is the percent composition of Cu in terms of these two isotopes?}

Step-by-Step Solution

Answer

69.152%→63Cu
 30.848%→65Cu

Step1: Explanation:

As you may know, the average atomic mass of an element is calculated by taking the weighted average of its naturally occurring isotopes.

Simply put, an element's naturally occurring isotopes add to the element's average atomic mass in proportion to their abundance.

avg. atomic mass=∑i(isotopei×abundancex)

Step 2: Continuation:

When it comes to the actual calculation, decimal abundances, which are simply percent abundances divided by 100, are preferable.

You're probably aware that copper has two naturally occurring isotopes: copper-63 and copper-65. This indicates that the sum of their decimal abundances must equal 1.

If x represents the decimal abundance of copper-63, then the decimal abundance of copper-65 will be equal to 1- x.

Step 3: calculation: