This document contains notes on electrochemistry from the IEB SAGS. It also includes all the IEB SAGS definitions as well as very thorough explanations about the concepts in this section.
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
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