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Title: Redox reaction- easy to understand ( for IB, A-level or Uni)
Description: The 4 pages note gives an easy to understand view of the redox reaction in bullet points. Explanation of the electrolysis and examples are also given. Advantages and disadvantages of electrolysis are also included.
Description: The 4 pages note gives an easy to understand view of the redox reaction in bullet points. Explanation of the electrolysis and examples are also given. Advantages and disadvantages of electrolysis are also included.
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Redox reaction
Oxidation
Reduction
gain O2
lose O2
Lose electron
gain electron
increase – O
...
A
( oxidized , reducing agent)
(reduced, oxidizing agent)
O
...
Element (O2,N2)
0
GRP 1 METAL
+1
GRP 2 Metal
+2
Common oxidizing and reducing agent
Oxidizing (reduced)
Acidify with sulphuric acid—XHCl, XHNO3
Acidified potassium
MnO4- > Mn2+
permanganate
Purple >
(KMnO4)
pink/colourless
Acidified potassium
Cr2O72-> Cr3+
dichromate
Orange > green
(K2Cr2O7)
Dilute
NO3-> NO
HNO3 (very strong)
(colourless)
Metal:
e
...
Cu (need heat)
NO REACTION WITH HCL
( non-oxidizing acid)
- NO gas
- NO2 evolve at the mouth of the
test tube
2NO + O2 > 2NO2 (BROWN)
Conc
...
H2SO4
(98% acid)
sulphuric acid
H2SO4 > SO2 (choking)
(colourles)
Dilute H2SO4
Oxidizing agent
### Chlorine
* chlorine as stronger
oxidizing agent that
displaces others
1
...
KI
Metals:
-NO2 ( + H2O)
Non-metals:
(HOT)
1
...
S>SO2 (
...
- all metals ( X Au, Pt)
- to (-)SO42- + SO2
- non-metal
C—( CO2 + SO2+ H20)
S ----( 3SO2 + H2O)
Only metals above Cu
# oxidizing agent – H+
Cl2 + 2Br > 2Cl- + Br2
(colourless > yellowish brown)
# solvent =heptane (upper)
solute= bromine ( lower)
# orange-red – extract most of
the bromine
aqueous layer(H20) =solvent
solute= bromine (lower)
Cl2+ 2I- > 2Cl- + I2 (brown)
(very pale green)
1
...
bromine
2
...
acidified K2Cr2O7
Sulphur dioxide
SO2> SO22-
Redox in chemical cell
Zinc-carbon cell – 1
...
zinc dissolves gradually
-zinc cup becomes thinner – electrolyte may leak
2
...
operate continuously – produce a steady supply of electricity
2
...
non-polluting – only product is water
Disadvantages:
1
...
very expensive – metals n liquefied gases (high pressure needed )
Uses :
1
...
Backup power source
- low level of noise + air pollution
- heat water
3
...
graphite electrode
anode : OH- > H20 + O2
cathode: Cu
# blue colour fades gradually --- eventually becomes sulphuric acid
2
...
electroplating – protect against corrosion + improve appearance
electrolyte > cointain ions of the plating metal
e
...
= Cu, Ni, chromium , Tin, Gold ,Silver
# NON-METAL : sprayed with a layer of carbon graphite ( plastic , glass)
# current X too high > loose spongy metal deposit > may peel off
2
...
reducing harmful waste
- chromate in chromium plating
- replace by chromium compounds
2
...
Treating effluents before discharge
- neutralization
acidic- sodium carbonate / slaked lime
alkaline > sulphuric acid
- precipitation of heavy metal ions
as insoluble hydroxides or carbonates – filtered off
> using sodium hydroxide/ sodium carbonate
- chromium waste
- chromate ions >reduced > chromium ions
- precipitated > chromium hydroxide
Title: Redox reaction- easy to understand ( for IB, A-level or Uni)
Description: The 4 pages note gives an easy to understand view of the redox reaction in bullet points. Explanation of the electrolysis and examples are also given. Advantages and disadvantages of electrolysis are also included.
Description: The 4 pages note gives an easy to understand view of the redox reaction in bullet points. Explanation of the electrolysis and examples are also given. Advantages and disadvantages of electrolysis are also included.