2.4 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 an isotope?

Back

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Front

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

Back

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

Front

If an isotope has a mass of 10 amu and is 50% abundant, what is its contribution to the average atomic mass?

Back

5 amu (10 amu * 0.50).

Front

What is the average atomic mass of an element with two isotopes: 10 amu (20% abundance) and 12 amu (80% abundance)?

Back

11.6 amu (10 amu * 0.20 + 12 amu * 0.80).

Front

What is the average atomic mass of an element with three isotopes: 75 amu (30% abundance), 76 amu (50% abundance), and 77 amu (20% abundance)?

Back

76.4 amu (75 amu * 0.30 + 76 amu * 0.50 + 77 amu * 0.20).

Front

What is the average atomic mass of an element with isotopes of 20 amu (10% abundance) and 22 amu (90% abundance)?

Back

21.8 amu (20 amu * 0.10 + 22 amu * 0.90).

Front

What is the average atomic mass of an element with isotopes of 14 amu (50% abundance) and 16 amu (50% abundance)?

Back

15 amu (14 amu * 0.50 + 16 amu * 0.50).

Front

What is the average atomic mass of an element with isotopes of 12 amu (25% abundance), 14 amu (50% abundance), and 16 amu (25% abundance)?

Back

14 amu (12 amu * 0.25 + 14 amu * 0.50 + 16 amu * 0.25).