All topics for all of the AQA AS-Level Chemistry papers, including all the practicals and their methods. Also includes some useful tips on exam technique and lots of worked exemplars to apply concepts!
Subatomic Charge Mass
particles
Proton +1 1
1.1 ATOMIC STRUCTURE Neutron 0 1
Electron -1 Approx.
0
Mass Number •Sum of protons & neutrons in the nucleus of an atom
Atomic Number •Number of protons in the nucleus of an atom
Relative Molecular •Average mass of 1 atom of an element relative to
Mass (Ar) 1/12 of he mass of 1 atom of Carbon-12
•Average mass of 1 molecule relative to 1/12 of the
Molar Mass (Mr) mass of 1 atom of Carbon-12
•Atoms of the same element with the same atomic
Isotope number (Ar) but different mass number (Mr)
Mass Spectrometry
VAPORISATION
heat sample to a gas in vaporisation chamber
IONISATION
sample bombarded with high speed/high energy e's from electron gun - turned
into positive ion by knocking off an electron.
ACCELERATION
Positive ion accelerated by negative plates into a beam of positive ions.
DEFLECTION
Positive ion deflected by electromagnets. Deflection depends on m/z ratio
DETECTION
Positive ion hits detecor, picks up e's from detector Mass spec connected to amplifier which is connected
(electron transfer) and generates a current. Size of current
proportional to abundance. to a computer that plots a chart (mass spectrum)
, 7
working out
structure of organic 6
Relative Abundance
molecules 5
4
identifying 3
used for measuring
elements &
Ar 2
isotopes
1
measuring
relative 0
abundance a b m/z ratio
c d e
Molecular ion - largest
m/z ratio
Ionisation • energy required to remove 1 mole of
Energy (ΔHi) electrons from 1 mole of gaseous atoms.
Shell closest to
e.g Boron (2,3)Title nucleus (2
7 electrons) higher
6 ΔHi
5
4 Different shell further
Δ Hi
3 from nucleus, lower
2 ΔHi
1
0
a b c d e General trend down the group
No of e's removed
first ionisation energy
kjmol-1
DOWN THE GROUP
Ionisation energy decreases because
there are more shells/more shielding.
Therefore outer e’s are further from
nucleus so less energy required to atomic number
remover outermost e.
•ΔHi increases across a period
•Same no. of shells, same shielding but
ΔHi Across a period (period 3) nuclear charge increasing so e's held
6
1 more tightly
5 •Al has an electron in 3p orbital
which is higher energy than the 3s
4 orbital (furhter from nucleus) so
2 less energy required to remove it.
ΔHi
3
2 • In P each 3p orbital contains 1 electron
whereas in S, one of the 3p orbitals
contains 2 electrons.
1
3 • Repulsion between these paired electrons
makes it easier to remove one of them
0
Na Mg AL Si P S Cl Ar
, 1.2 AMOUNT OF SUBSTANCE
Molecular
• Actual
number
of
each
type
of
atom
Formula
in
a
compound
Empirical
• Simplest
whole
number
ratio
of
Formula
atoms
in
a
compound
Avogadro's
• 6x1023
no.
of
atoms
of
12C
in
12g
of
constant
the
12C
isotope.
• Amount
of
substance
that
contains
the
Mole
same
no.
of
particles
as
there
are
atoms
of
12C
in
12g
of
the
12C
isotope.
𝑚𝑎𝑠𝑠
𝑚𝑜𝑙𝑒𝑠 =
𝑀𝑟
Empirical formula
Atoms X Y 𝑀𝑟
𝑀𝐹 =
% mass 𝑀𝑎𝑠𝑠 𝑜𝑓 𝐸𝐹
Moles
Simplest Ratio
then multiply EF by ^ to get
MF.
moles
Solid
moles
=
mass/Mr
volume
x
molarity
MOLE
Vol = m
3
Liquid
Gas
moles
=
vol.
x
PV=nRT
conc.
Temp = K
3
-3
Dm
Mol dm Pressure = N = moles
Pa
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