moles and Avogadros constant.
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What is the mole?
The amount of a substance that contains the same number of atoms or particles as 12g of carbon 12
What is the value of the mole?
6.02x10^23 (avogadro’s constant)
What is molar mass?
The mass of one mole of a substance
What is an example of Mr?
Carbon = 12 Oxygen = 16 Nitrogen = 14
What does the molar mass do?
It takes the same value as the atomic mass and helps calculate for Moles = mass/ molar mass
What is the units of molar mass?
G/mol
When 0.22g of pure barium is added to water, how many moles of Barium have been added?
Moles = mass/mr = 0.22/137.33 =16 x10^-4
Modern pencils contain graphite rather than lead. In a pencil containing 0.642g of pure graphite, a form of carbon, calculate the amount in mol of graphite. Using Avogadro’s constant, calculate how many carbon atoms are present in this sample of graphite.
Moles=mass/mr =0.642/12 =0.0535 0.0535 x (6.02x10^23) =3.22x10^22