Question

A sample of an oxide of iron was found to contain 72.34% by mass of iron and 27.66% by mass of oxygen. What is the empirical formula for this compound? (The correct answer is Fe3O4, but I’m not sure how to do the math)

Answer 1

Assume 72.34 g 27.66 g Fe = Atom Fe Notes Mass in g 27.660 72.340 Molar Mass in g/mol Moles of atom = Mass in g / Molar Mass (g/mol) 55.8 16 72.340 55.8 27.660 16 Divide mass with molar mass Convert Mass to moles 1.296 1.729 = Divide the all mole values with small value to get simplest Simplest ratio 1.296 1.729 1.296 1.296 ratio 1.000 1.333 Nearest whole number 4.0005 Multiply with 3 3 to get nearest whole number Whole number 3 4 so we get Fe = O= 4 = ; so emeperical Formual = Fe304 We get Fe-3 and O= 4