Using the example above as a guide, calculate the atomic mass of sulfur if

95.00% of all sulfur atoms have a mass of 31.972 amu
0.76% have a mass of 32.971 amu
4.22% have a mass of 33.967 amu
Question 10 options:

69.765 amu

56.865 amu

34.313 amu

32.057 amu

3 answers

To calculate the atomic mass of sulfur, we can use the weighted average formula:

Atomic mass = (% of isotope 1 × mass of isotope 1) + (% of isotope 2 × mass of isotope 2) + (% of isotope 3 × mass of isotope 3)

Plugging in the given values:

Atomic mass = (95.00% × 31.972 amu) + (0.76% × 32.971 amu) + (4.22% × 33.967 amu)

Atomic mass = (0.9500 × 31.972 amu) + (0.0076 × 32.971 amu) + (0.0422 × 33.967 amu)

Atomic mass ≈ 30.373 + 0.2510076 + 1.433274

Atomic mass ≈ 32.057 amu

Therefore, the atomic mass of sulfur is approximately 32.057 amu.
Using the example above as a guide, calculate the average atomic mass for the mystery element shown below. Use that value to identify the element on the periodic table.

one has a mass of 30.973 amu and 99.0% abundance
one has a mass of 31.973 amu and 0.8% abundance
one with a mass of 26.973 amu and 0.2% abundance
Calculate the average atomic mass to determine which which element this is.

Question 11 options:

Phosphorus

Sulfur

Chlorine

Iron
To calculate the average atomic mass for the mystery element, we can use the same weighted average formula as before:

Average atomic mass = (% of isotope 1 × mass of isotope 1) + (% of isotope 2 × mass of isotope 2) + (% of isotope 3 × mass of isotope 3)

Plugging in the given values:

Average atomic mass = (99.0% × 30.973 amu) + (0.8% × 31.973 amu) + (0.2% × 26.973 amu)

Average atomic mass = (0.990 × 30.973 amu) + (0.008 × 31.973 amu) + (0.002 × 26.973 amu)

Average atomic mass ≈ 30.663 + 0.255784 + 0.053946

Average atomic mass ≈ 30.97273 amu

Therefore, the average atomic mass for the mystery element is approximately 30.97273 amu. Comparing this value to the atomic masses on the periodic table, we find that this value matches the atomic mass of Phosphorus (P) closely, which is 30.97376 amu. Therefore, the mystery element is most likely Phosphorus.