Transcript C2 3.2 Masses of atoms and moles

C2 3.2
Masses of atoms and moles
Equations show how many atoms of reactants
are needed to make the products ( not masses)
Mg
+
2HCl
MgCl2 +
When ions form
the mass of any
change in electrons
is ignored
H2
( 1.0 x 10-30 Kg )
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
12
carbon atom
6 C
mass = 12
23
11
7
3
Na
Li
mass = 23
mass = 7
C2 3.2
Masses of atoms and moles
Relative formula mass (Mr) or mole
eg
water
H
2
And finally:
1 mole of any element
or compound always contains
the same number of particles
( atoms ions or molecules)
O
6.02 x 10
23
avogadro’s number
(1x2)g
+
16g
Write down the RAMs
=
Relative formula mass
18 g
or 1 mole of water molecules
has a mass of 18 g
Carbon-12
atomic
number
atomic
elements
one
24 + (2x19) = 62
16 : 24
=
16/16
: 24/16
1 : 1.5
divide by smallest!