C2 3.2 Masses of atoms and moles

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C2 3.2 Masses of atoms and moles
When ions form the mass of any change in
electrons is ignored ( 1.0 x 10-30 Kg )
Equations show how many atoms of reactants are
needed to make the products ( not masses)
Mg 2HCl MgCl2 H2
The relative atomic mass (Ar) in grams is
called a mole of the substance ( actual mass of
a proton or a neutron is 1.6 x 10-27 Kg
) The mass of an atom is compared to a carbon
atom 12 6
mass 12
23 11 mass 23
Na
C
7 3 mass 7
Li
2
C2 3.2 Masses of atoms and moles
And finally 1 mole of any
element or compound always contains the same
number of particles ( atoms ions or molecules)
6.02 x 10 23 avogadros
number
Relative formula mass (Mr) or mole eg
water H 2 O

( 1 x 2 ) g
16g
Write down the RAMs

Relative formula mass or 1 mole of water
molecules has a mass of 18 g
18 g
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Carbon-12
atomic
number
atomic
elements
one
24 (2x19) 62
16 24 16/16 24/16
divide by smallest!
1 1.5