Question

A compound contains 69.94 percent iron and 30.06 percent oxygen. What is its molecular formula if the molar mass of the compound is 199.55 grams per mole?

Answer 1

The molecular formula is Fe₂O₃

Step-by-step explanation:

The molar mass of the compound is 199.55 g/mol; this means that if we have 1 mol of the compound, we'd have 199.55 g, we'd also have:

• 199.55 * 69.96/100 = 139.57 g of iron

• 199.55 * 30.06/100 = 59.98 g of oxygen

Now we calculate the moles of each element present in the given masses, using their atomic masses:

• 139.57 g Fe ÷ 55.84 g/mol = 2.50 mol Fe

• 59.98 g O ÷ 16 g/mol = 3.75 mol O

Then in 1 mol of the compound, there's 2.50 mol Fe and 3.75 mol O:

• Fe₂.₅O₃.₇₅

We convert the coefficients into integers (Divide them by the lowest number among them and multiply them by two):

• Fe₂O₃