This document discusses three topics related to chemistry: 1) The contact process for producing sulfuric acid, which involves burning sulfur to produce sulfur dioxide, purifying and oxidizing the SO2 to form sulfur trioxide using a catalyst, absorbing the SO3 in sulfuric acid to form oleum, and then diluting the oleum to produce sulfuric acid. 2) Hydrogen sulfide, its properties as a colorless, flammable, and poisonous gas, and its acidity when dissolved in water. 3) Different types of lead pigments used to color paints, including white lead, red lead, chrome yellow, chrome red, and litharge, along with their compositions and methods of

1. CHEMISTRY XII

2. 
 WASIF
 M.HASAN
 IJLAL QASIM
.
GROUP
MEMBERS

3. CONTENT TABLE:
1.CONTACT
PROCESS
3.LEAD
PIGMENT
2.HYDROGEN
SULPHIDE

4. 1.CONTACT PROCESS:
PRINCIPLE:
‘It is based on the principle of the oxidation of SO2 into SO3
Using solid catalyst (V2O5) followed by its absorptiion in
H2SO4 give oleum which that dissolves in water to give
H2SO4.’

5.  STEP1(FORMATION OF SO2)
Firstly SO2 is produced by burning
Sulphur in pyrite burner.
4FeS2 + 11O2 2Fe2O3
 STEP2 (PURIFICATION OF
SO2)
8SO2
In the second step SO2 is purified from impurities by passing
through following chamber
1) Dust filter chamber
2) Washing tower
3) Drying tower
4) Arsenic PurifierSO2 is washed, dried and purified through
the dust, filter, washing, drying tower, Arsenic purifier.

6.  STEP3(OXIDATION OF SO2)
This purified by mixture of SO2 and air is then passed through
Contact tower where it is oxidized to SO3 in the presence of
catalyst V2O5 at 450-500C .
2SO2 + O2 2SO3
 STEP4(FORMATIOPN OF OLEUM)
The oxidized So2 (So3) is them brought to absorption tower
where it is absorbed by concentrated H2So4 to form Oleum
(pyrosulphuric acid )
SO3 + H2SO4 H2S2O7

7.  STEP5(CONVERISON OF H2S2O7 TO H2SO4)
Oleum is then carried to Dilution Tower where H is absorbed in calculated amount of
water to get acid of required concentration.
H2S2O7 + H2O 2H2SO4

8. • INTRODUCTION:
2.HYDROGEN
SULPHIDE:
 Hydrogen sulphide is a colourless chalcogen hydride gas with the formula H2S.
However, it is a highly corrosive, flammable and poisonous gas.
 Hydrogen sulphide is most commonly formed due to the microbial breakdown of
organic matter in the absence of oxygen.

9. • PROPERTIES:
 Chemical formula: H2S
 Molar mass: 34.08 g·mol-1
 Appearance: Colourless gas
 Odour: Pungent, like that of rotten eggs
 Density: 1.363 g dm-3
 Melting point: −82 °C (−116 °F; 191 K)
 Boiling point: −60 °C (−76 °F; 213 K)
 Solubility in water: 4 g dm-3 (at 20 °C)
 Vapour pressure: 1740 kPa (at 21 °C)

10. • CHEMICAL PROPERTIES:
1) ACIDIC PROPERTY :
It is soluble in water and it's solution is acidic in nature
H2S + H2O HS + H3O
2) COMBUSTION :
It burns with blue flames in air to form SO2 and H2O.
2H2S + 3O2 → 2H2O + 2SO2
• STRUCTURE:
The hydrogen sulphide having sp3 hybridization and having bond angle 92.1 and the shape is tetrahedral.

11. " Lead forms various types of pigment which are
used to give proper colour to paint."
3.LEAD PIGMENT:
:
Type Of
Pigments
1.White Lead
Pigment
2.Red Lead Pigment
(Sandhur)
3.Chrome Yellow
Pigment
4.Chrome Red
pigment

12. 5. Turner’s Yellow Pigment
6. Litharge (Mudra Sang OR Massicot)
1.White lead Pigment:
It is Basic lead Carbonate and has approximately
composition as [2PbCO3.Pb(OH)2] or Pb3 (OH)2(CO3)2. it is known as
hydrocerussite.
A)BY CHAMBER OR DUCH PROCESS:
Mixture of acetic acid and steam is passed though lead sheets when
White Lead is obtained.
 2Pb+2CH COOH+2H20[Pb(OH),Pb(CH,COO),] +2H2
USES:
It is also poisonous hence in recent year while lead
Has been replaced by Titanium Dioxide (TIO2).

13. 2.Red lead pigment :
It is called as Triplumbic tetraoxide or lead sesqui oxide and its
composition is Pb3O4 OR (2PbO.PbO2).It is also known as Sandhur and Minium.
PREPARATION:
It is prepared by heating lead monoxide (Litharge) in a revolving
furnace with access of air about 450C.
6Pb0+ 0₂ 450°C 2Pb,0
Uses:
 It is use in glass industries for making Glazes.
3.Chrome Yellow Pigment :
It is lead chromate .It is yellow colored pigment with composition PbCrO4
(Lead Chromate) .It occur in nature as Crocoite.
PREPARATION:
It is prepared by mixing dilute solution Pb(NO3)2 and K2CrO4.
Pb(NO3)2+K2CrO4 → PbCrO4+2KNO3
USES:
It is used in paint which is used for making roads and it is also used for
making green paints.

14. 4.Chrome Red Pigment:
It is basic lead Chromate and its composition is PbCrO4.PbO or Pb2CrO5.
PREPARATION:
It is prepared by Digesting lead Chromate with NaOH.
2PbCr04,+ 2NaOH→ Na2CrO4+Pb2CrO5+ H2O
Uses:
It is dark Red Pigment and is used in paints.
5. Turner's yellow Pigment:
It’s composition is PbCl2.4PbO.
PREPARATION:
It is prepared by boiling the solution of sodium chloride with Litharge (PbO) and then
heating to solid products.
5Pb0+H2O+2NaCI→ 2NaOH+ PbCl2.4Pbo
6.Litharge: It is also a lead pigment.It’s color is red or yellow depending on the mode of
preparation.Red lead monoxide is known as Murda Sang and yellow lead monoxide is called
Massicot.
Uses: It is used for making Varnishes,plaster and enamels. It is used in manufacture of Red
lead and flint glass.

15. You can ask if you have any queries.