Section 2.5 Worksheet - class practice assignment PDF

Preview

Summary

class practice assignment...

Description

Atomic Masses Learning Objectives 

Define atomic mass and atomic mass unit.



Calculate average atomic mass.

Define atomic mass and atomic mass unit. 1. Define atomic mass. Why is it considered a weighted average? 2. What is an atomic mass unit? 3. What is the atomic mass of zinc in atomic mass units?

4. What is the atomic mass of barium in atomic mass units? 5. Which has more mass—1 tungsten atom or 11 oxygen atoms? 6. Which has more mass—1 magnesium atom or 6 helium atoms?

Calculate average atomic mass. 7. Calculate the average atomic mass of copper. Copper exists as a mixture of 2 isotopes. Their respective masses and natural abundance are shown below. 1. 63Cu: 62.930 u (69.17%) 2.

65

Cu: 64.928 u (30.83%)

8. What is the average mass of a single magnesium atom in grams?



ANSWER KEY 1. The atomic mass is an average of an element’s atomic masses, weighted by the natural abundance of each isotope of that element. It is a weighted average because different isotopes have different masses. 2. An atomic mass unit is 1/12th of the mass of a 12C atom. 3. 65.38 u 4. 137.33 u 5. 1 W atom = 183.84 u > 11 oxygen atoms = 11 x 16.0 = 176.0 u 6. 1 Mg atom = 24.31 u > 6 He atoms = 6 x 4.00 u = 24.00 u. 7. 63.546 u 8. 4.04 x 10-23 g...