
CALCULATIONS BASED ON FORMULAE
7.2  Mole Concept
The scientific definition of a mole is as follows:
 1 mole
of ^{12}C is exactly 12 grams.
(in section 3.2 we learned that carbon12
is a naturally occurring isotope of carbon)
 1 mole of any substance contains 6.022 x 10^{23} particles (rounded
to 4 significant figures).
In the above definition, do you realize
that when we talk about the mole,
 it has an equivalent mass (1 mole = 12 grams ^{12}C)
 it is a counting unit, a quantitiy of things (1 mole of any substance contains
6.022 x 10^{23 } particles)
Want to see this number written out in loonng
form?
Click
here.
Why do we use the mole as a counting unit?
4 good reasons!
 In chemistry, the particles that make up matter are
very small (section
3.1). So, counting by the mole is convenient.
 We need to scale
up to see what we are working with.
 We need to scale
up to do laboratory work.
 In chemistry, we count
by weighing.
Section
8.1
Calculation
of Mole of Units. Avogadro's Number (N) ..p189
