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4. Redox
oxidation is the process of electron loss: reduction is the process of electron gain:
Zn Zn2+ + 2e- Cl2 + 2e- 2Cl-
It involves an increase in oxidation number It involves a decrease in oxidation number

Rules for assigning oxidation numbers
eg . Zn, Cl2, O2, Ar all…

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Balancing Redox equations
Writing half equations
1. Work out oxidation numbers for element being oxidised/ reduced Zn Zn2+ Zn changes from 0 to +2

2. Add electrons equal to the change in oxidation number
For reduction add e's to reactants
Zn Zn2+ + 2e-
For oxidation add e's to products…

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11. Spectroscopy
Mass spectroscopy Mass spectrum for butane
The peak with the highest
When organic molecules are 43 mass/charge ratio will be normally
passed through a mass due to the original molecule that
spectrometer, it detects both hasn't fragmented (called the
the whole molecule and molecular ion) . As the…

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use spectra to identify particular functional groups and to identify
impurities, limited to data presented in wavenumber form

Spectra for



Spectra for
O-H absorptions tend ethanoic acid
to be broad




"rogue" absorptions can also occur and…

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1. Energetics
Definition: Enthalpy change is the amount of heat energy taken in
If an enthalpy change occurs then energy is

system and
transferred between
or given out during any change in a system provided the
surroundings . The system is the chemicals
is constant and the surroundings is…

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Calculating the enthalpy change of reaction, Hr from experimental data
The heat capacity of water is
General method 4.18 J g-1K-1. In any reaction
where the reactants are
1. Using q= m x cp x T calculate energy change for quantities used dissolved in water we assume
that the heat…

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Hess's Law
Hess's law is a version of the first law
Hess's law states that total enthalpy change for a reaction is of thermodynamics, which is that
independent of the route by which the chemical change takes place energy is always conserved.

Using Hess's law to determine enthalpy changes of…

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Example 6. Using the following combustion data to calculate the heat of formation of propene
3C (s) + 3H2 (g) C3H6 (g)
Hc C (s) = -393kJ mol-1 Hc H2 (g)= ­286 kJ mol-1 Hf C3H6(g)= ­-2058 kJ mol-1

H = Hc reactants - Hc products

Hf = 3 x…

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More complicated examples that may occur at AS

Working out Hf of a compound using bond energies and other data This is a more complicated
example of the type in example 8

elements Compound in
The H's can be
standard state
combinations of
H to turn to different data

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2. Kinetics
Collision theory
Reactions can only occur when collisions take place between particles
having sufficient energy. The energy is usually needed to break
the relevant bonds in one or either of the reactant molecules.
This minimum energy is called the Activation Energy

The Activation Energy is defined as the…



Amazing! Thank you :)

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