Calculating 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?

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?

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

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.

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What is relative abundance?

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The percentage of a particular isotope in a naturally occurring sample of an element.

Front

If an isotope has a mass of 39.946 amu and an abundance of 4.35%, what is its contribution to average atomic mass?

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0.39 amu (calculated as 39.946 * 0.0435).

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What is the average atomic mass of an element with two isotopes: 75% of mass 12 amu and 25% of mass 14 amu?

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Average Atomic Mass = (12 * 0.75) + (14 * 0.25) = 12.5 amu.

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What is the significance of average atomic mass in chemistry?

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It helps predict the behavior of elements in chemical reactions and is used in stoichiometry.

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How does the abundance of isotopes affect average atomic mass?

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Higher abundance of a heavier isotope increases the average atomic mass, while higher abundance of a lighter isotope decreases it.

Front

What is the average atomic mass of thallium (Tl) with isotopes Tl-203 (29.5%) and Tl-205 (70.5%)?

Back

204.41 amu.