Chemistry Unit 2 Notes

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Energetic Kinetics
Enthalpy Change(DH) is the heat energy change measured Collision Theory
under conditions of constant pressure Reactions can only occur when collisions
take place between particles having sufficient energy
Standard enthalpy changes refer to standard
conditions, i.e. 100 kPa and a stated temperature Activation energythe minimum energy required for a
(e.g. DH298) reaction to occur
standard enthalpy of formationthe enthalpy change when Rate of reactionthe rate of change of the concentrations
one mole of a compound is formed from its elements in of the reactants (or products) with time.
their standard states under standard conditions
Equilibria
standard enthalpy of combustionthe enthalpy change when
Le Chatliers principleany equilibrium system when
one mole of a substance is completely burnt in oxygen
subjected to change will move the equilibrium system as to
under standard conditions
minimise the change
Hess LawThe enthalpy change for a chemical reaction is
independent of the route taken
Dynamic equilibrium rate forward reaction =
Mean bond enthalpyaverage value of the bond rate backward reaction concentration remains
dissociation enthalpy for a given type of bond taken from
constant
a range of different compounds
Redox Reactions Group 7, the Halogens
oxidation is the process of electron loss Electronegivity of the halogens decrease down the group
oxidising agents are electron acceptors As the number of shells increases, the shielding increases
reduction is the process of electron gain and the electrons in the covalent bond are further from
reducing agents are electron donors (and more shielded from) the nucleus. Therefore they are
less strongly attracted to the nucleus and the
electronegativity decreases.
H=1 (except in metal hydrides e.g. NaH where its The melting and boiling points of the halogens increase
-1), group 1 always 1, group 2 always 2,Al always steadily down the group. This is due to the increase in
3, O is -2 (except in peroxides where its -1 and strength of the Van Der Waal's forces between the
compounds with OF2 where its 2), F=-1, Cl=-1 molecules, which results from the increasing number of
(except with F and O where its 1) electrons in the molecule and the increasing surface area of
the molecule.
Oxidisng power decreases down the group
Reducing power increases down the group
H2SO4+NaX gives HX+NaHSO4
Ag+(aq) + Cl(aq) AgCl(s)white precipitate, dissolves in
dilute NH3
Ag+(aq) + Br(aq) AgBr(s)cream precipitate dissolves in
conc. NH3
Ag+(aq) + I(aq) AgI(s)yellow precipitate, insoluble in
conc. NH3
Cl2(g) + H2O(l) == HCl(aq) + HClO(aq) (Chloric
acidbleach)
Cl2(g) + 2OH(aq) Cl(aq) + ClO(aq) + H2O(l)
Cl2(g) + 2NaOH(aq) NaCl(aq) + NaOCl(aq) + H2O(l)
Test for Cl2 turns damp red litmus paper red (due to HOCl
and HCl), then bleaches it to white (due to Cl2)
H2SO4 + 2H+ + 2e SO2 + 2H2O
H2SO4 + 6H+ + 6e S + 4H2O
H2SO4 + 8H+ + 8e H2S + 4H2O

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Group 2, the Alkaline Earth Metals Extraction of Metals
Melting point decreases down the group, increase sulfide ores are usually converted into
in size of atom so weaker attraction by the nucles oxides by roasting in air e.g.…read more

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Alkenes (mostly electrophilic addition) Alcohols
know that alkenes are unsaturated hydrocarbons Aldehydes and Ketones are carbonyl compoundsthey
know that bonding in alkenes involves a double covalent have functional group C=O their general formula is
bond CnH2nO
know that the arrangement >C=C< is planar Aldehydes has suffix ­al and they have a hydrogen and
understand that EZ isomers exist due to restricted one alkyl group attached to carbonyl carbon atom
rotation
about the C=C bond
understand that the double bond in an alkenes is a centre…read more

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