More information on molar mass and molecular weight

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.

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.

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.

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.

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.

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.

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 well-defined isotopes. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass.

Thank you so much Dr. qasim fadil for responding to my question. I appreciate the effort you have put in to obtain the information.

Dear Laghrib,

If I am not wrong, your problem is you may have some precursor or other material still existing in your powder, and so you cannot weight your powder. One way is to follow the stoichiometry of which you synthesized TiO2. Moreover, after calcination in a proper temperature (according to phase you want to obtain or required temperature to remove precursor), you may conduct XRD analysis to see if the powder is well crystalline and does not have any amorphous material. Then, if the only indexed crystalline phases would be Anatase or Rutile, then you can estimate the weight of your powder by weighting it considering the density difference between Anatse and Rutile.