AP Calculating Avg. Atomic Mass

Front

What is average atomic mass?

Back

The weighted average of the masses of an element's isotopes, taking into account their relative abundances.

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How do you calculate average atomic mass?

Back

Multiply the mass of each isotope by its relative abundance (as a decimal), then sum these values.

Front

What is the formula for calculating average atomic mass?

Back

Average Atomic Mass = (mass1 * abundance1) + (mass2 * abundance2) + ...

Front

If an isotope has a mass of 10.012 amu and an abundance of 20%, what is its contribution to the average atomic mass?

Back

Contribution = 10.012 amu * 0.20 = 2.0024 amu.

Front

What is the average atomic mass of an element with two isotopes: 10.012 amu (20% abundance) and 11.009 amu (80% abundance)?

Back

Average Atomic Mass = (10.012 * 0.20) + (11.009 * 0.80) = 10.812 amu.

Front

What is the average atomic mass of an element with isotopes of 75.23 amu (24.1%), 74.61 amu (48.7%), and 75.20 amu (27.2%)?

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Average Atomic Mass = (75.23 * 0.241) + (74.61 * 0.487) + (75.20 * 0.272) = 74.92 amu.

Front

What is the significance of the atomic mass unit (amu)?

Back

It is a standard unit of mass that quantifies mass on an atomic or molecular scale, defined as one twelfth of the mass of a carbon-12 atom.

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What does it mean if an isotope is more abundant?

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It means that a larger percentage of the element's atoms are of that particular isotope, affecting the average atomic mass.

Front

What is an isotope?

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Atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different masses.

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How does the abundance of isotopes affect average atomic mass?

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Higher abundance isotopes have a greater impact on the average atomic mass than less abundant isotopes.