How many moles are in 239 g of iron? Express your answer to three significant figures.

Question

If someone could just show me the steps so I can practice solving by myself. Online classes have been very difficult.

Answer 1

Hey there!

The way you want to solve problems like this is by using the molecule's molar mass, or atomic mass. You can find each element's molar mass on the periodic table, usually right below the scientific name or the atomic number. To find the molar mass of the molecule, you just multiply the molecular weight (atomic mass) of each element by the amount of atoms of that element in the molecule.

Examples:

O - 16g/mol

O₂ - 32g/mol

C₂H₄ - 28g/mol (molar mass of carbon is 12, molar mass of hydrogen is 1, so 12*2+ 1*4 = 28g/mol)

Fe (iron) - 55.845 g/mol ; This tells us that every mole of iron weighs, on average, 55.845grams

If we have 239 grams of iron, and we know that one mole is equal to 55.845 grams, we can do dimensional analysis to convert the grams to moles using the molar mass.

239g / 55.845g/mol = 4.28 moles