Mole is a counting device or a number like:
12 things = Dozen
144 things = Gross
2 things = Pair
1000 g = 1k g
similarly:
6.022 x 1023 particles =1 mole
Mole Definition:
In Chemistry , mole is defined as the amount of substance that exactly contains 6.022 x 1023 particles. .
For Example:
12g C-atom = 1 mole carbon = 6.022x 1023 C -atoms
18g H2O molecule = 1 mole carbon = 6.022x 1023 H2O molecule
58.5g NaCl Formula unit = = 1 mole carbon = 6.022x 1023 NaCl Formula unit
17 g OH-1 ions = 1 mole carbon = 6.022x 1023 OH-1 ions
so the mole is also defined as:
Atomic mass, molecular mass and formula mass when expressed in grams is equal to one mole.
e.g.
Atomic mass of carbon atom = 12 amu
Atomic mass when expressed in grams =12g= 1 mole
Molecular mass of water molecule = 18 amu
Molecular mass when expressed in grams =18g= 1 mole
Formula mass of NaCl = 58.5amu
Formula mass when expressed in grams = 58.5g=1mole
Avogadro’s number:
Avogadro’s number is defined as the number Of 6.022 x 1023 particles present in one mole of a substance.
Avogadro’s number is denoted by NA .
NA = 6.022 x 1023 particles =1 mole
Formulas to calculate number of moles and Avogadro‘s number of particles:
No of moles = mass
molar mass
Number of moles = Number of particles
6.022 x 1023
No of moles of gas at STP = volume of gas at STP
molar Volume
No of particles = Moles X Avogadro’s number
Mass of a substance = no of moles x Molar mass
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