Relative formula
mass can be found by adding up the mass numbers
A mole is a precise
number. When you get precisely that number of atoms or molecules, of
any element or compound, they weight exactly the same number of grams
as the relative atomic mass, Ar of the element or
compound. One mole of atoms or molecules of any substance will have a
mass in grams equal to the relative formula mass for that substance.
Example- Carbon has
an Ar of 12 and so the one mole of carbon weighs exactly
12g.
The number
6.023x1023 is called Avogadro's number or the Avogardo
constant. So you can think of a mole as the Avogardo number of
particles in a substance, where the articles are atoms, molecules,
ions or electrons.
Number of moles =
Mass in g/ Mr
One mole of
any gas always occupies 24dmº
(=24000 cmº)
at room temperature and pressure (RTP: 25ºc
and 1 atmosphere)
Volume
(dm3)
= moles of gas x 24
Volume
(dm3)
= (mass of gas/ Mr
of
gas) x 24
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