The
'mole'
A mole is the Avogadro number of particles.. rather like a dozen is twelve of whatever, the mole is just that, an Avogadro number of whatever - I quite fancy a mole of pennies (or even better pounds!)! The chemists define the Avogadro Number in terms of carbon 12 atoms: the number of carbon-12 atoms in 12 grams (0.012 kg) of unbound carbon-12 in its rest-energy electronic state. The Avogadro number is a big number 6.02 x 10 23 = 602 000 000 000 000 000 000 000 = six hundred and two thousand, million, million, million! It is given the symbol NA (NumberAvogadro)
by physicists and L (because in German scientific literature, sometimes also known as the Loschmidt constant) by chemists. The link between mass and number of particles is simple: The mass of one particle (smallest unit - atom or molecule) expressed in grams contains NA particles. eg.
Try the following questions:1. How many atoms of lead are found in a 2mg sample ? (atomic mass of lead is 210g) ? Answer 2. What would be the mass of one hundred million million
(100 000 000 000 000 = 1014) atoms of Uranium 238 (atomic
mass is 238)?
Answer |
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