Quiz on Atomic Mass and Isotopes

What is the average atomic mass?

• The sum of the masses of all isotopes

• The weighted average of the mass of isotopes in a naturally occurring sample of an element

• The mass of the most abundant isotope

• The average mass of the isotopes found in a laboratory

What is the second step in determining the average atomic mass?

• Add up all the products of the fractional abundance and mass of the isotope

• Multiply the fractional abundance by the mass of the isotope

• Turn the percent abundance into a decimal number

• Find the mass on the periodic table

What is the percent abundance of Zinc-66?

• 48.89%

• 27.81%

• 4.11%

• 18.57%

Which isotope of Zinc has the lowest percent abundance?

• Zinc-64

• Zinc-66

• Zinc-67

• Zinc-70

How many isotopes of Zinc are listed in the table?

• 3

• 4

• 5

• 6

If Carbon has two isotopes, Carbon-12 and Carbon-13, with percent abundances of 98.89% and 1.11% respectively, what is the first step to find the average atomic mass?

• Add the masses of Carbon-12 and Carbon-13

• Multiply the percent abundances by the masses of Carbon-12 and Carbon-13

• Convert the percent abundances to fractional abundances

• Find the mass of Carbon on the periodic table

What is the percent abundance of Carbon-13 in Example 2?

• 98.89%

• 1.11%

• 50%

• 100%

Find the average atomic mass of iodine if it consists of 80% iodine-127, 17% iodine-126, and 3% iodine-128.

• 126.7 amu

• 127.0 amu

• 126.9 amu

• 127.1 amu

Calculate the average atomic mass of iron if 15% of the iron found in nature is 55Fe and 85% of the iron found in nature is 56Fe.

• 55.85 amu

• 55.15 amu

• 56.00 amu

• 55.50 amu

Calculate the average atomic mass of nitrogen given the following isotopic masses and natural percents of abundance: nitrogen-14 (95%), nitrogen-15 (3%), and nitrogen-16 (2%).

• 14.07 amu

• 14.03 amu

• 14.10 amu

• 14.00 amu