University:
Eastern Kentucky University
Course:
CHE 111 | General Chemistry
Academic year:

2021
Views:

431

Pages:

2
Author:

Lance Gutierrez

Name _____________________________ Calculating Average Atomic Mass Worksheet Show ALL calculation setups. 1. The term “average atomic mass” is a __weighted_______________________average, and so is calculated differently, from a “normal” average. Explain how this type of average is calculated. This average is calculated by summing masses of the element's isotopes. (Abundance/100 x Mass then add the masses together) ----------------------------------------------------------------------------------------------------------------------------------2. The element Copper has naturally occurring isotopes with mass numbers of 63 and 65. The relative abundance and atomic masses are: 69.2% for mass of 62.93u 30.8% for mass of 64.93u. Calculate the average atomic mass of Copper. Show ALL work for full credit. 69.2/100 x 62.93 = 43.54756 30.8/100 x 64.93 = 19.99844 ggghvhvhvhvhhv= 63.546uggg ----------------------------------------------------------------------------------------------------------------------------------3. Calculate the average atomic mass of Sulfur if: 95.00% of all Sulfur atoms have a mass of 31.972 u, 0.76% has a mass of 32.971u and 4.22% have a mass of 33.967u. Show ALL work for full credit. 0.95 x 31.972 = 30.3734 0.0076 x 32.971 = 0.251 0.0422 x 33.967 = 1.433 7777777777775 = 32.0574 u ------------------------------------------------------------------------------------------------------------------------------------4. Naturally occurring Strontium consists of four isotopes, Sr-84, Sr-86, Sr-87 and Sr-88. Below is the data concerning Strontium: Sr-84 0.56% Sr-86 9.86% Sr-87 7.00% Sr-88 82.58% What is the average atomic mass of Strontium? Show ALL work, for full credit. 0.0056(84) + 0.0986(86) + 0.07(87) + 0.8258(88) = 87.7104 u --------------------------------------------------------------------------------------------------------------------------------------5. Calculate the average atomic mass of Bromine. Show ALL work, for full credit. One isotope of Bromine has an atomic mass of 78.92u and a relative abundance of 50.69%. The other major isotope of Bromine has an atomic mass of 80.92u and a relative abundance of 49.31%. (0.5069)(78.92) + (0.4931)(80.92) = 79.9062 u