Average Atomic Mass Practice

The atomic mass of an element is the ___.

• average of the mass number and the atomic number for the element

• weighted average of the masses of the isotopes of the element

• total mass of the isotopes of the element

• total number of subatomic particles in the nucleus

If an element has two isotopes with masses 10 amu and 12 amu, and their abundances are 25% and 75% respectively, what is the average atomic mass of the element?

• 13 amu

• 10.5 amu

• 11.5 amu

• 9 amu

If an element has two isotopes with masses 5 amu and 7 amu, and their abundances are 40% and 60% respectively, what is the average atomic mass of the element?

• 5.6

• 6.8

• 7.5

• 6.2

Lithium has two naturally occurring isotopes, ⁶Li (6.0151 amu) is 7.500% and the abundance of ⁷Li (7.0160 amu). is 92.5%. What is the average atomic mass of Lithium?

• 6.0750 amu

• 6.0902 amu

• 6.9250 amu

• 6.9409 amu

Calculate the average atomic mass of silver.

• 106.38649amu
• 111.91896amu
• 107.8677amu
• 121

An isotope has three forms.  30% have a mass of 4 amu, 20% have a mass of 5 amu and 50% have a mass of 3 amu.  Average atomic mass will be closest to

• 2 amu
• 3 amu
• 4 amu
• 5 amu

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?

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

Compute the average atomic mass for silicon:

• 27.977
• 28.09
• 28.976
• The average mass cannot be determined from provided information.

Four isotopes of lead include lead-204, lead-206, lead-207, and lead-208.  The average atomic mass of lead is 207.2.  Which isotope of lead is likely to be the most abundant.

• 204
• 206
• 207
• 208

What is the name of the atom pictured here?

• Nitrogen
• Nitrogen-15
• Nitrogen-7
• Nitrogen-8