Question

An iron sulfide compound is analyzed, and found to contain 11.26 g iron and 9.70 g sulfur. Determine the molar ratio of sulfur to iron in this compound, and hence its chemical formula.

Answer 1

• Molar ratio = 1.5

• Chemical formula = Fe₂S₃

Step-by-step explanation:

First we convert the given masses of each element into moles, using their respective molar masses:

• Fe ⇒ 11.26 g ÷ 55.845 g/mol = 0.202 mol Fe

• S ⇒ 9.70 g ÷ 32.065 g/mol = 0.302 mol S

Now we divide them in order to calculate the molar ratio of S to Fe:

• 0.302 / 0.202 = 1.5

Meaning that for each 1 Fe mol, there's 1.5 S moles. We can write that as Fe₁S₁.₅

Finally we double those subscripts so that they become the lowest possible integers: Fe₂S₃.