Question

The atom percent of Fe in pyrrhotite of composition $Fe_{0.77}S$ is ________. (Round off to two decimal places)

Answer 1

Correct Answer: 43.49

Calculating the Atom Percent of Fe in Pyrrhotite (FeS) 

Step 1: Understand the Formula

The formula for pyrrhotite is FeS, which contains one atom of iron (Fe) and one atom of sulfur (S).

Step 2: Molar Mass Calculation

To calculate the atom percent of iron (Fe), we need the molar masses of Fe and S:

• The molar mass of Fe is approximately 55.85 g/mol.
• The molar mass of S is approximately 32.07 g/mol.

Step 3: Calculate the Number of Moles

Using the formula FeS, we calculate the number of moles of Fe and S:

• The number of moles of Fe in FeS is 0.77 moles.
• The number of moles of S is 1 mole (since the formula has 1 sulfur atom).

Step 4: Calculate the Atom Percent of Fe

The formula for calculating the atom percent of Fe is:

\[ \text{Atom percent of Fe} = \frac{0.77}{0.77 + 1} \times 100 = 43.51\% \]

Final Answer:

Thus, the atom percent of Fe in pyrrhotite is 43.51%.