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). However when talking about a mole of an ionic compound we will still use the term molar mass. 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. Use the periodic table to find the molar mass of hydrogen, H. For nitrogen, the mass of the N 2 molecule is simply (14.01 + 14.01) = 28.02 amu. Masses of Atoms are Expressed in Atomic Mass Units (amus) a. For a molecule (for example, nitrogen, N 2) the mass of molecule is the sum of the atomic masses of the two nitrogen atoms. 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. According to the periodic table, 1 mol of U has a mass of 238.03 g, so the mass of 2 mol is twice that, or 476.06 g. 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. The periodic table shows that the atomic mass (rounded to two decimal points) of Al is 26.98, so 1 mol of Al atoms has a mass of 26.98 g. By definition, the molar mass of carbon-12 is numerically the same, and is therefore exactly 12 grams. The mass exactly equal to one twelfth the mass of an atom of carbon-12 Atomic mass (in amu). We have defined a mole based on the isotopic atomic mass of carbon-12. Because of that old definition, we were able to say that all those atomic weights are in grams per mole of substance or abbreviated g/mol. Average Atomic Mass Atomic mass unit (amu). 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. ) a carbon atom with six proton and six neutrons in its’ nucleus, surrounded by six electrons.
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