Iron oxide molar mass
Molar mass of FeO = 71.8444 g/mol
Molecular weight calculation:
55.845 + 15.9994
Element  Symbol  Atomic Mass  # of Atoms  Mass Percent 
Fe  55.845  77.730%  
15.9994  22.270% 
In chemistry, the formula weight is a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a chemical formula by the number of atoms of that element present in the formula, then adding all of these products together.
A common request on this site is to convert grams to moles. To complete this calculation, you have to know what substance you are trying to convert. The reason is that the molar mass of the substance affects the conversion. This site explains how to find molar mass.
Formula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction. These relative weights computed from the chemical equation are sometimes called equation weights.
Using the chemical formula of the compound and the periodic table of elements, we can add up the atomic weights and calculate molecular weight of the substance.
If the formula used in calculating molar mass is the molecular formula, the formula weight computed is the molecular weight. The percentage by weight of any atom or group of atoms in a compound can be computed by dividing the total weight of the atom (or group of atoms) in the formula by the formula weight and multiplying by 100.
The atomic weights used on this site come from NIST, the National Institute of Standards and Technology. We use the most common isotopes. This is how to calculate molar mass (average molecular weight), which is based on isotropically weighted averages. This is not the same as molecular mass, which is the mass of a single molecule of welldefined isotopes. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass.
Finding molar mass starts with units of grams per mole (g/mol). When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula.
You might also like
Carnelian Tangerine Quartz Crystal Cluster Specimen in Silver Ore Deposit (Missletoe Mine #1 Magdelena, NM). (hematite infused Quartz Specimen) Small Cabinet size: 3"x 2.5"x 3.5" Weight: 10.2OZ Carnelian (also spelled cornelian) is a brownishred mineral which is commonly used as a semiprecious gemstone. Similar to carnelian is sard, which is generally harder and darker (the difference is not rigidly defined, and the two names are often used interchangeably). Both carnelian and sard are varieties of the silica mineral chalcedony colored by impurities of iron oxide. The color can vary greatly, ranging from pale orange to an intense almostblack coloration. It is most commonly found in Brazil, India, Siberia, and Germany. Jewelry (Mother Earth Magdelena, NM.)
