Average Atomic Mass Quiz

24.1% of all the isotopes of a an element have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 27.2% have a mass of 75.20 amu. What is the average mass of this element?

Show your work.

• 74.92 amu
• 24.97 amu
• 75.01 amu
• 74.51 amu

Nitrogen has three occurring isotopes: Nitrogen-13, Nitrogen-14, Nitrogen-15. The average atomic mass of Nitrogen is 14.007 amu. Which isotope is the most abundant?

• Nitrogen-13

• Nitrogen-14

• Nitrogen-15

• Based on the information given, it cannot be determined

Naturally occurring chlorine that is used in swimming pools is chlorine-35 with a relative abundance of 0.7553 and chlorine-37 with a relative abundance of 0.2447. Calculate the average atomic mass and show your work.

• 35.49 amu

• 35.00 amu

• 37.00 amu

• 17.49 amu

What is the mass number of this isotope?

• 1

• 3

• 4

• 7

Magnesium exists as the three isotopes shown. What is the average atomic mass of magnesium?

Show your work.

• 20.74 amu

• 22.56 amu

• 18.39 amu

• 24.31