Calculating Average Atomic Mass Worksheet Answer Key

When it comes to chemistry, one of the key concepts that students need to understand is how to calculate the average atomic mass of an element. This involves knowing the isotopic masses and abundances of the different isotopes of an element. In this worksheet answer key, we will go through some practice problems to help you master this important skill.

Problem 1: Calculate the average atomic mass of Carbon (C)

Carbon has two isotopes: Carbon-12 and Carbon-13. The abundance of Carbon-12 is 98.9%, and its atomic mass is 12.0000 u. The abundance of Carbon-13 is 1.1%, and its atomic mass is 13.0034 u. To calculate the average atomic mass of Carbon, we use the formula:

Average Atomic Mass = (Abundance of Isotope 1 * Atomic Mass of Isotope 1) + (Abundance of Isotope 2 * Atomic Mass of Isotope 2)

Calculating Average Atomic Mass Worksheet Answer Key

= (0.989 * 12.0000) + (0.011 * 13.0034)

= 11.868 + 0.143

= 12.011 u

Therefore, the average atomic mass of Carbon is 12.011 u.

Problem 2: Calculate the average atomic mass of Chlorine (Cl)

Chlorine has two isotopes: Chlorine-35 and Chlorine-37. The abundance of Chlorine-35 is 75.53%, and its atomic mass is 34.9689 u. The abundance of Chlorine-37 is 24.47%, and its atomic mass is 36.9659 u. To calculate the average atomic mass of Chlorine, we use the same formula as before:

Average Atomic Mass = (Abundance of Isotope 1 * Atomic Mass of Isotope 1) + (Abundance of Isotope 2 * Atomic Mass of Isotope 2)

= (0.7553 * 34.9689) + (0.2447 * 36.9659)

= 26.4247 + 9.0401

= 35.4648 u

Therefore, the average atomic mass of Chlorine is 35.4648 u.

Problem 3: Calculate the average atomic mass of Neon (Ne)

Neon has three isotopes: Neon-20, Neon-21, and Neon-22. The abundance of Neon-20 is 90.48%, and its atomic mass is 19.9924 u. The abundance of Neon-21 is 0.27%, and its atomic mass is 20.9938 u. The abundance of Neon-22 is 9.25%, and its atomic mass is 21.9914 u. To calculate the average atomic mass of Neon, we use the same formula as before:

Average Atomic Mass = (Abundance of Isotope 1 * Atomic Mass of Isotope 1) + (Abundance of Isotope 2 * Atomic Mass of Isotope 2) + (Abundance of Isotope 3 * Atomic Mass of Isotope 3)

= (0.9048 * 19.9924) + (0.0027 * 20.9938) + (0.0925 * 21.9914)

= 18.0780 + 0.0566 + 2.0323

= 20.1669 u

Therefore, the average atomic mass of Neon is 20.1669 u.

Problem 4: Calculate the average atomic mass of Copper (Cu)

Copper has two isotopes: Copper-63 and Copper-65. The abundance of Copper-63 is 69.17%, and its atomic mass is 62.9296 u. The abundance of Copper-65 is 30.83%, and its atomic mass is 64.9278 u. To calculate the average atomic mass of Copper, we use the same formula as before:

Average Atomic Mass = (Abundance of Isotope 1 * Atomic Mass of Isotope 1) + (Abundance of Isotope 2 * Atomic Mass of Isotope 2)

= (0.6917 * 62.9296) + (0.3083 * 64.9278)

= 43.5390 + 20.0358

= 63.5748 u

Therefore, the average atomic mass of Copper is 63.5748 u.

Problem 5: Calculate the average atomic mass of Argon (Ar)

Argon has three isotopes: Argon-36, Argon-38, and Argon-40. The abundance of Argon-36 is 0.34%, and its atomic mass is 35.9675 u. The abundance of Argon-38 is 0.06%, and its atomic mass is 37.9627 u. The abundance of Argon-40 is 99.6%, and its atomic mass is 39.9624 u. To calculate the average atomic mass of Argon, we use the same formula as before:

Conclusion

Calculating the average atomic mass of an element is an important skill in chemistry. By understanding the isotopic masses and abundances of different isotopes, you can determine the overall atomic mass of an element. Practice problems like the ones in this worksheet answer key can help you master this concept and excel in your chemistry studies.