Thus, the formula mass of calcium hydrogen carbonate is 117.10 amu and the molar mass of calcium hydrogen carbonate is 117.10 grams per mole (g/mol). From moles to mass (grams): Multiply your initial mole value by the molar mass of the compound as determined by the periodic table. Molar mass is typically expressed in either gram ( g) or kilograms (kg).
Multiply the subscript (number of atoms) times that element’s atomic mass and add the masses of all the elements in the molecule to obtain the molecular mass. The periodic table lists the atomic mass of carbon as 12.011 amu. Find the atomic mass for each element using the mass shown in the Periodic Table or Atomic Weight Table. The molar mass of any substance is its atomic mass, molecular mass, or formula mass in grams per mole. However when talking about a mole of an ionic compound we will still use the term molar mass. From mass (grams) to moles: Divide your initial mass by the molar mass of the compound as determined by the periodic table. In each case, the number of grams in 1 mol is the same as the number of atomic mass units that describe the atomic mass, the molecular mass, or the formula mass, respectively. This is because there are no individual molecules in ionic compounds. For compounds that are not molecular (ionic compounds), it is improper to use the term “molecular mass” and “ formula mass” is generally substituted. The molar mass of the N 2 molecule is therefore 28.02 g/mol. This is referred to as the molecular mass and the molecular mass of any molecule is simply the sum of the atomic masses of all of the elements in that molecule. For nitrogen, the mass of the N 2 molecule is simply (14.01 + 14.01) = 28.02 amu. Now, you know the atomic number of sodium is 11, so you may wonder why the molar mass is not exactly 22 (11 protons and 11 neutrons). The relative atomic mass is the same as the molar mass (except molar mass is in g/mol). For a molecule (for example, nitrogen, N 2) the mass of molecule is the sum of the atomic masses of the two nitrogen atoms. Do this by looking up sodium (Na) on the periodic table. The concept of molar mass can also be applied to compounds. Further, if you have 16.00 grams of oxygen atoms, you know from the definition of a mole that your sample contains 6.022 x 10 23 oxygen atoms. For example, the atomic mass of an oxygen atom is 16.00 amu that means the molar mass of an oxygen atom is 16.00 g/mol. It is also sometimes called: Molecular Mass, Molecular Weight, Formula Mass, or Formula Weight. One atomic mass unit (u) is equal to 1/12 the mass of one atom of carbon-12. Generalizing this definition, the molar mass of any substance in grams per mole is numerically equal to the mass of that substance expressed in atomic mass units. Molar mass is the mass (in atomic mass units) of one mole of a of a substance. By definition, the molar mass of carbon-12 is numerically the same, and is therefore exactly 12 grams. We have defined a mole based on the isotopic atomic mass of carbon-12. The atomic mass of an element is the relative average of all of the naturally occurring isotopes of that element and atomic mass is the number that appears in the periodic table. The molar mass of a compound is the mass in grams of 1 mole of that substance, a property expressed in units of grams per mole (g/mol)īecause the definitions of both the mole and the formula mass are based on the same reference substance, 12C, the molar mass of any compound is numerically equivalent to its formula weight in amu.) a carbon atom with six proton and six neutrons in its’ nucleus, surrounded by six electrons. The masses of 1 mole of different compunds, however, are different, since the masses of the individual molecules are drastically different. The given mass of K (4.7 g) is a bit more than one-tenth the molar mass (39.10 g), so a reasonable ballpark estimate of the number of moles would be slightly greater than 0.1 mol.
Similar to atoms, 1 mole of any compound contains the same number of molecules as 1 mole of any other compund. Referring to the periodic table, the atomic mass of K is 39.10 amu, and so its molar mass is 39.10 g/mol.