Molar Masses of Elements
The molar mass of atoms of an element is given by the atomic weight of the element multiplied by the molar mass constant, M
u = 1×10−3 kg/mol = 1 g/mol:
- M(H) = 1.007 97(7) × 1 g/mol = 1.007 97(7) g/mol
- M(S) = 32.065(5) × 1 g/mol = 32.065(5) g/mol
- M(Cl) = 35.453(2) × 1 g/mol = 35.453(2) g/mol
- M(Fe) = 55.845(2) × 1 g/mol = 55.845(2) g/mol.
Multiplying by the molar mass constant ensures that the calculation is dimensionally correct: atomic weights are dimensionless quantities(i.e., pure numbers) whereas molar masses have units (in this case, grams/mole).
Some elements are usually encountered as molecules, e.g. hydrogen (H
2), sulfur (S
8), chlorine (Cl
2). The molar mass of molecules of these elements is the molar mass of the atoms multiplied by the number of atoms in each molecule:
- M(H
2) = 2 × 1.007 97(7) × 1 g/mol = 2.015 88(14) g/mol - M(S
8) = 8 × 32.065(5) × 1 g/mol = 256.52(4) g/mol - M(Cl
2) = 2 × 35.453(2) × 1 g/mol = 70.906(4) g/mol.
Read more about this topic: Molar Mass
Famous quotes containing the words masses and/or elements:
“There is but little virtue in the action of masses of men. When the majority shall at length vote for the abolition of slavery, it will be because they are indifferent to slavery, or because there is but little slavery left to be abolished by their vote. They will then be the only slaves. Only his vote can hasten the abolition of slavery who asserts his own freedom by his vote.”
—Henry David Thoreau (18171862)
“The popularity of that baby-faced boy, who possessed not even the elements of a good actor, was a hallucination in the public mind, and a disgrace to our theatrical history.”
—Thomas Campbell (17771844)