IEB Grade 12 Electrochemistry notes

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1. 1 Definitions
Redox reaction transfer of electrons
: a reaction
involving the

Oxidation : loss of electrons

Reduction
gain of electrons
:




Oxidising agent : a substance that accepts electrons

Reducing agent : a substance that donates electrons




1. 2 Half reactions
-




Oxidation half reaction

µ →
Mt + e
reducing it left M
agent

Reduction half reaction
-




N + e → N
oxidising} it is
adding to N
agent


the oxidation states of metals and non
1. 3 Recognising metals
-




Oxidation states of metals

Fe )
" "
Zero oxidation state =
solid metals ( Nd Ag Cu
, , ,
In ,



" "
Fe )
Agt Fest
2T
positive oxidation state =
ions in solution ( Nat , ,
Cu ,
Zn . ,
-




part of a salt




Oxidation states of non -

metals
" "
Zero oxidation state ( C1 2,02 Hz )
,




positive / oxidation state ICI 05 Ht part of )
-




negative a salt in a solution
-




,




1. 4
Examples of redox reactions

1. 2N ( s ) + CUZ ( Ag ) +
→ CU (s) +
Znzt ( ag )

CU 1st
Agt ( ag ) 2
Ag ( S )
+
2 .
+ 2 → CUZ lag I +

,1. 5 Standard Electrode Potentials (SEP) table

,2. Half Cells -
*
spectator ions d not take part in the electron transfer
2. 1 Structure of Half Cells -




↳
half -
cell consists of an electrode dipped into an electrical
conducting solution (electrolyte)
↳ an is a substance that can conduct
electrolyte electricity by forming free ions when molten

or dissolved in solution

↳ enters / leaves an
an electrode is a conductor
through which
electricity object substance
,




or region (made of metal /
graphite)
↳ a
half cell -


will contain an element in two different oxidation states 12 different charges )
↳
an equilibrium will exist between the two oxidation states




2. 1 Gas Half cells

↳ consist of with its ions
a
gas in equilibrium
↳
gas is pumped into the cell in a
glass tube which has a piece of platinum in

it ( the electrode)
↳
gas absorbs onto ( sticks onto the surface of) the platinum foil as well as
bubbling
the solution
through
↳ the actual electrode is the platinum wire not the
gas


2. 3 The Standard Hydrogen Electrode (SHE/
↳ a
hydrogen half -

cell which is assembled under standard conditions which ,
are :



-
Concentration of solutions : 1 MOI dm-3 .




-

Temperature 25°C :




-
Pressure of gases : 1 Atm

( H2 ) bubbled
of hydrogen gas g hydrogen
↳ consists
through an
electrolyte contain ions

( Ht ) under standard solutions
↳a
platinum ( Pt ) electrode is used as it is unreactive and takes no part in the reaction

↳ Pt electrode provides a metal surface where redox reactions can take place