# Edexcel U1 - EVERYTHING in 8 pages

bascially pretty much as it says on the tin. i missed out the reaction mechanisms as they where to complex for a word doc.

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Chemical quantities and formulae
Definitions
Elements are substance which cannot be broken down by chemical means into other
substances
Atoms are the smallest part of any element that can take part in chemical reaction
Ions are formed when an atom gains or loses electrons ­ charged particles
Compounds are formed when two or more elements are chemically attached
Molecule is the smallest part of a covalent compound or an element that can exist
alone
Empirical formulae is the simplest atom ratio of the elements of a compound
Step Method Example
C H O
Mass or Percentage 40% 6.67% 53.33
1 Molar Mass 12 1 16
Divide by smallest 3.33 6.67 3.33
2 3.33 3.33 3.33
value
Input whole number
3 1 2 1
ratio to formulae
CH2O
Molecular formulae the exact number of atoms /ions that make up a compound exact
multiple of its empirical formula
Molecular Mass
Empirical formula Mass X Empirical formula
Balancing equations and ionic equations
Include ions in ionic equations which have changed state from one side of the
equation to the other
The rest of the molecules are spectator ions which are not involved with the reaction
1. Put state symbols and show separate ions
Fe(s) + Cu2+ (aq) + SO42(aq) Cu(s) + Fe2+ (aq) + SO42(aq)
2. Remove spectator ions
Fe(s) + Cu2+ (aq) Cu(s) + Fe2+ (aq)
3. Balance out charges isn't necessary in this reaction
Half equations would show the molecules/ions which change oxidation state and you
balance charges with electrons
E.g. Cu2+ (aq) + 2e Cu(s)
Fe(s) Fe2+ (aq) + 2e
Solution calculations: n = c x v and amounts of substance with n = Mr m
number of parts in chemical
Concentrations can be expressed as Parts per million = number of parts it is contained in (amount
by volume or mass)
Avogadro's constant is the number of atoms in exactly 12g of carbon12 which equals
6.02 x 1023
can also show how many particles in a given number of moles of a solid or gas
moles x (6.02 x 1023)
Chemical equations can be used to determine the masses of reactants and vice versa, the
mass of reactants can confirm a balanced equation

## Other pages in this set

### Page 2

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Practice the calculations
Reactions with gases
Molar volumes is the volume occupied by 1 mol of any gas= 24dm3 at standard
pressure and temp
Ratio of gas volumes used to calculate reacting masses.
E.g. 6dm3 of methane = 24 6 = 1 molar volume
4
Also able to find chemical equations from experimental data as volumes of gases as
s.t.p are proportional to their amount
E.g. 4.5 dm3 oxygen 3 dm3 nitrogen

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Between a systems and surroundings
H = HProducts Hreactants
Enthalpy level diagrams show relative energy levels of reactants and products
Exothermic reactions have a negative H and give out energy into surroundings
Endothermic reactions have a positive H and take in energy from surroundings
Reactants Products
Products Reactants
Definitions
H°f is when 1 mole of compounds is formed from its constituent elements
= products reactants
H°c is when 1 mole substance is completely burnt in oxygen
= reactants products
H°at is when 1 mole of…read more

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They are average values which may be different in certain environments
Values given are gaseous bond enthalpies
o If a liquid is in the calculation the energy of vapourization must be included.…read more

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Na [1s12s22p63s1]
1st ionization energy trend increases across a
period but decreases down a group.
Evidence for electron subshells
Drop between Be and B show that B has
a new subshell which is less stable and
therefore more easily ionized.
N has relatively high ionization energy
due to it having a half full subshell which

### Page 6

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Electron density maps will show separate ions with zero density between
Electrolysis and separate attraction to anode and cathode
Ions try and achieve noble gas configuration (octet rule or isoelectronic) either as an anion (+)
by gaining electrons or a cation (+) by losing electrons
Dot and cross diagrams (easy)
IONIC LATTICES are formed when each ion is surrounded by an oppositely charged ion can
also produce a giant ionic structure
Cations < Anions
Increases down a group due to the…read more

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Covalent bond is the strong electrostatic attraction between the nucleus' of the two atoms
involved and the shared pair of electrons
Dative covalent bond are formed when both shared electrons are from one atom
Double/triple bonds
Lone pairs of electrons affect the shape of the molecule as they contribute to areas of

### Page 8

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Cl + CH3 CH3Cl
CH3 + CH3 C2H6
Alkenes are unsaturated HC's which contain double bonds, general formula is CnH2n
CarbonCarbon double bonds have a sigma and pi bond and are not rotational
o p orbitals overlap to produce 2 areas of
electron density, above and below the sigma
bond
these bonds produce geometric isomers depending
on the functional groups and what side of the double
bond they exist on
Cis Trans Isomerism. Cis = same side, Trans = different.…read more

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Potassium manganite (VII) reacts the same way, decolorized with the presence of

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