The factor-label method yields the desired cancellation of units, and the computed result is on the order of 10 22 as expected. These relative weights computed from the chemical equation are sometimes called equation weights.\] For example, if we are trying calculate for ammonia (NH 3 ), then we. The atomic mass is equal to the atomic number which is listed below the element symbol.
Now, compute the sum of products of number of atoms to the atomic weight: Molar mass (Cl 2) Count i Weight i. Molar Mass of Ammonia NH 3 Step 1: The first step for calculating molar mass is to identify all the elements in a given molecule and write their atomic masses using the periodic table. Then, lookup atomic weights for each element in periodic table: Cl: 35.453. 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.įormula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction. First, compute the number of each atom in Cl 2: Cl: 2. 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. If the formula used in calculating molar mass is the molecular formula, the formula weight computed is the molecular weight. Options for hiding the symbol or name of the elements provide a handy learning aid for memorizing the periodic table. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula. Molar mass can be calculated by using the periodic table and following three simple steps. Use this periodic table for calculating molar mass for any chemical formula. When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass.įinding molar mass starts with units of grams per mole (g/mol). This is not the same as molecular mass, which is the mass of a single molecule of well-defined isotopes. This is how to calculate molar mass (average molecular weight), which is based on isotropically weighted averages.
The atomic weights used on this site come from NIST, the National Institute of Standards and Technology. Add up all and assign unit as grams/mole. Multiply the atomic weight of each element with its number of atoms present in the compound.
This site explains how to find molar mass. Make use of the chemical formula to determine the number of atoms of each element in the compound. The reason is that the molar mass of the substance affects the conversion. Interactive periodic table with up-to-date element property data collected from authoritative sources.
To complete this calculation, you have to know what substance you are trying to convert. 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.Ī common request on this site is to convert grams to moles.