Average Atomic Mass

What subatomic particles would you find in the nucleus of an atom?

• Protons only
• Protons and Neutrons
• Neutrons and Electrons
• Protons and Electrons 

4.35% of all X atoms have a mass of 40 amu. 83.79% have a mass of 42 amu, 9.50% have a mass of 43 amu, and 2.36% have a mass of 44 amu. What is the average atomic mass of atom X? Round to the nearest hundredth.

• 42.06 amu

• 42.19 amu

• 10.432 amu

• 42.0552 amu

Compute the average atomic mass for silicon:

• 27.977 amu

• 28.09 amu

• 28.976 amu

• The average mass cannot be determined from provided information.

Calculate the average atomic mass of the element iron (Fe) using the following data:

[Isotope / % abundance]

[Iron 54 / 6% ] [Iron 56 / 92% ] [ Iron 57 / 2% ]

• 53.7 amu

• 54.9 amu

• 5592.0 amu

• 55.9 amu

Isotopes of an element have a different number of...

• Protons

• Neutrons

• Electrons

• Mass

There are two primary isotopes found in any sample of copper: copper-63 and copper-65. The isotope ⁶⁵Cu composes 69.2% of the sample and ⁶³Cu comprises the other 30.8%. Based on this data, what is the atomic mass of copper?

• 29 amu

• 63.546 amu

• 64.4 amu

• 63.6 amu

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

An element has two naturally occurring isotopes. One is 10.013 amu and is 19.9% abundant. The other is 11.01 amu and is 80.1% abundant. What is the average atomic mass? What element is it?

• 9.012, Beryllium
• 12.011, Carbon
• 6.941, Lithium
• 10.812, Boron

If an element has three isotopes with masses 30 amu, 32 amu, and 34 amu, and their abundances are 25%, 50%, and 25% respectively, what is the average atomic mass of the element?

• 33

• 35

• 32

• 31

If an element has two isotopes with masses 8 amu and 10 amu, and their abundances are 60% and 40% respectively, what is the average atomic mass of the element?

• 8.8 amu

• 10.4 amu

• 9.6 amu

• 9.2 amu