Average 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.

Front

How do you calculate average atomic mass?

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Average atomic mass = (fraction of isotope 1 × mass of isotope 1) + (fraction of isotope 2 × mass of isotope 2) + ...

Front

What is an isotope?

Back

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

Front

What does amu stand for?

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Atomic mass unit, a standard unit of mass used to express atomic and molecular weights.

Front

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

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Average atomic mass = (0.75 × 10) + (0.25 × 12) = 10.5 amu.

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What is the significance of relative abundance in calculating average atomic mass?

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Relative abundance indicates how common each isotope is in nature, affecting the overall average mass.

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What is the average atomic mass of an element with isotopes of 20 amu (50%) and 22 amu (50%)?

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Average atomic mass = (0.50 × 20) + (0.50 × 22) = 21 amu.

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What is the average atomic mass of an element with isotopes of 35 amu (20%) and 37 amu (80%)?

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Average atomic mass = (0.20 × 35) + (0.80 × 37) = 36.6 amu.

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What is the average atomic mass of an element with isotopes of 40 amu (10%), 41 amu (30%), and 42 amu (60%)?

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Average atomic mass = (0.10 × 40) + (0.30 × 41) + (0.60 × 42) = 41.2 amu.

Front

What is the average atomic mass of an element with isotopes of 75 amu (24.1%), 74.6 amu (48.7%), and 75.2 amu (27.2%)?

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Average atomic mass = (0.241 × 75) + (0.487 × 74.6) + (0.272 × 75.2) = 74.92 amu.