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Chemistry Cheat Sheet (DRAFT) by

Cheat Sheet for things I forget

This is a draft cheat sheet. It is a work in progress and is not finished yet.

CaO Cycle

CaCO
3
⇒
CaO + CO
2
CaO + H
2
O
⇒
Ca(OH)
2
Ca(OH)
2
+ CO
2
⇒
CaCO
3
+ H
2
O

Eutrop­hic­ation

Eutrop­hic­ation arises from the oversupply of nutrients, which induces explosive growth of plants and algae which, when such organisms die, consume the oxygen in the body of water, thereby creating the state of hypoxia.

Reactivity Series

Pottasium
K
Sodium
Na
Calcium
Ca
Magnesium
Mg
Aluminium
Al
Zinc
Zn
Iron
Fe
Lead
Pb
Hydrogen
H
Copper
Cu
Mercury
Hg
Silver
Ag
Gold
Au
Reactivity increases upwards
More reactive a metal is, it will be less stable in its elemental form
Compounds of a more reactive metal will be more stable than the compounds of a less reactive metal

Extraction of Metals

The method of extraction of metals depends on the reactivity of the metal or the stability of the metal compound ( usually metal oxides or chlorides ).

There are three methods for the extraction of metals:
1. Electr­olytic Reduction of molten metal compounds.
2. Chemical reduction by heating metal oxide with carbon
3. Thermal Decomp­osition

K - Al by Method 1
Zn - Cu by Method 2
Hg - Ag by Method 3

Air Pollutants

Pollutant
Source
Effect
How to reduce?
CO
Incomplete combustion in car engines or furnaces
It forms carbox­yli­c-h­emo­globin and can cause death
Keep the car engine well tuned.
SO
2
/SO
3
Burning of coal & fossil fuels and volcanic eruptions
Can cause acid rain
Fuel should be desulf­urized.
N
x
O
y
Lightning and Car Engines
Causes acid rain and is irritant and causes rashes and breathing problems; asthma.
Using catalytic converter.

Fractional Distil­lation of Air

CO
2
and H
2
O and any dust particles are removed.
Air is cooled to -200oC. Air is liquified at this temper­ature
On increasing the temper­ature, N
2
boils off at -196oC, Ar at -185oC and O
2
at -183oC

Experi­mental Verifi­cation of Oxygen in Air

 
Diagram
Cu is heated
Plungers in A and B are moved back and forth so that air passes over Cu again and again until there is no decrease in volume
2Cu
(s)
+ O
2
⇒ heat
2CuO
(s)

Compos­ition of Air

Nitrogen
78% ≈ 80%
Oxygen
21% ≈ 20%
Other Gases
1%
 

Haber Process

N
2
Source
  
Fractional Distil­lation of air
H
2
Source
  
Oil or Natural Gas
Temper­ature
  
500oC
Pressure
  
200 - 250 atm
Catalyst
  
Powdered Iron(Fe)
N
2(g)
+ 3H
(g)
⇔
2NH
3(g)
Manufa­cture of Ammonia

Properties of Ammonia

Physical
Colourless Gas
Has pungent smell
Lighter than air; Mr = 17
Highly soluble in water
Weakly basic; Turns damped red litmus paper blue
Irritant and can cause rashes
Chemical
Dissolves in water to produce ammonium hydroxide
NH
3(g)
+ H
2
O
(l)
⇔
NH
4
OH
(aq)
Reacts with acids to produce salts
NH
3
+ HCl
⇒
NH
4
Cl
2NH
3
+ H
2
SO
4
⇒
(NH
4
)
2
SO
4
NH
3
+ HNO
3
⇒
NH
4
NO
3

Uses of Ammonia

A large amount of ammonia is used to make fertil­izers
An important lab reagent; Used to identify metal cations
Used to manufa­cture of Explosives
Used as a Refrig­erant
Used in Pharma­ceu­tical Industry
Used to manufa­cture cosmetics

Extraction of Iron

Ore
Haematite ( Fe
2
O
3
)
Method
2 ( refer to Extraction of Metals )
Reducing Agent
Carbon ( C )
Carbon Monoxide ( CO )
Chemical Reactions
in Blast Furnace
C + O`2
⇒
CO
2
CO
2
+ C
⇒
2CO
3C + 2Fe
2
O
3
⇒
4Fe + 3CO
2
3CO + Fe
2
O
3
⇒
2Fe + 3CO
2
Haematite contains sand ( SiO
2
) as impurity which is converted to slag ( floats on surfac­e ) by the following reaction
CaCO
3
⇒
CaO + CO
2
CaO + SiO
2
⇒
CaSiO
3
( slag )
Steel
Low carbon steel
  
upto 0.3% C
Medium carbon steel
  
0.4 - 0.6 % C
High carbon steel
  
0.7 - 1 % C

Rusting of Iron

Iron reacts with O
2
in presence of H
2
O ( mo­isture ) to form Fe
2
O
3
·XH
2
O ( rust )
Reaction is slow but is promoted in presence of any electr­olyte in water especially under acidic conditions
Prevention
Coating
Coating Iron with plastic, paint, oil or grease
Electroplating
Electr­opl­ating Iron with chromium, nickel, silver
Galvon­izing
Dipping in molten zinc to coat with zinc metal
Cathodic Protection
Connecting Iron body to negative terminal of a battery
Sacrif­icial Protection
Attaching Iron to a more reactive metal eg Mg or Zn
 

Properties of Sulfur

It is a yellow solid
It has a low melting point of 113oC
Found as a mineral
Burns with blue flames to produce SO
2
SO
2
is highly soluble in water
SO
2
can be further oxidized to SO
3
which causes acid rain
SO
3
+ H
2
O
⇒
H
2
SO
4

Contact Process

Burning of Sulfur to produce SO
2
S + O
2
⇒
SO
2
Catalytic oxidation of SO
2
to SO
3
2SO
2
+ O
2
⇔
2SO
3
600oC
1-2 atm
V
2
O
5
as catalyst
Making Oleum
SO
3
is dissolved in H
2
SO
4
to form Oleum (H
2
S
2
O
7
)
SO
3
+ H
2
SO
4
⇒
H
2
S
2
O
7
React with water
H
2
S
2
O
7
+ H
2
O
⇒
2H
2
SO
4
Manufa­cture of H
2
O
4
(Sulfuric Acid)

Extraction of Aluminium

Method
1 ( refer to Extraction of Metals )
Ore
Bauxite (Al
2
O
3
)
MP = 2000oC
 
To prevent to heating to such a large temper­ature, Bauxite is dissolved in molten Cryolite ( Na
2
AlF
6
) which melts at 900oC
Graphite electrodes are used.
 
At Cathode
Al3+ + 3e-
⇒
Al
(l)
   
MP = 660oC
At Anode
O2-
(l)
⇒
O + 2e-
O + O
⇒
O
2
 
Oxygen produced at anode reacts with C ( from the anode ) due to high temper­ature and produces CO or CO
2
Anode burns away and needs to be replaced period­ically

Properties and Uses of Aluminium

Light metal with high tensile strength
Very good conductor ( three valance electrons )
Can reflect light and heat radiation
Used in aircraft bodies
Used in circuit wires
Used in milk tanks
Cost of Al is high due to:
cost of electricut
 
cost of graphite anodes
 
cost of fuel to keep electr­olyte molten
Rusting
Al reacts with O
2
to form a non-porous Al
2
O
3
coating which seals Al inside