13b - sulfur
TRANSCRIPT
-
7/24/2019 13B - Sulfur
1/17
SULFUR
( eg SO2)
GROUP 16(AS)
-
7/24/2019 13B - Sulfur
2/17
Sources of SO2
1. From human activity : egs
a. combustion of fossil fuel/petroleum Proteins in plants and animals consist of
amino acids. Certain amino acids contains S
Eg : cystine and methionine
Plants & animals decaycompressed byhigh pressure & tempforms fossil fuel
Petroleum burned in airS oxidised to SO2
-
7/24/2019 13B - Sulfur
3/17
b. Contact process
c. manufacture of cement or bricks d. coal power stations
FeS present in coal is oxidised to SO2
CaO is used to absorb and prevent the SO2from being released into the atmosphere
-
7/24/2019 13B - Sulfur
4/17
2. From natural sources: egs
a. volcanoes b. rotting vegetation and plankton
-
7/24/2019 13B - Sulfur
5/17
Acid Rain
1. Role of SO2:
a. Acid rain: rain having pH less than 5.6 b. One of the chief culprit in formation of acid
rain is SO2released into the atmosphere
c. SO2+ moisture + O
2forms H
2SO
4
Eqn : 2SO2+ 2H2O + O22H2SO4
-
7/24/2019 13B - Sulfur
6/17
-
7/24/2019 13B - Sulfur
7/17
2. Effects of acid rain :
a. kills fishes in lakes :
SO4
2-in acid rain combines with aluminium
in complex compounds (eg clay) to form
solubleAl2(SO4)3
This washes into streams where it interferes with
the operation of fish gills which becomes cloggedwith mucus.
Fishes die from lack of oxygen
-
7/24/2019 13B - Sulfur
8/17
-
7/24/2019 13B - Sulfur
9/17
b. damage to trees and crops :
i) Al3+
poisons trees ii) essential nutrients are washed from soil.
Trees starve to death.
-
7/24/2019 13B - Sulfur
10/17
-
7/24/2019 13B - Sulfur
11/17
c. corrodes or damages
i) buildings ( contains limestone or marbleCaCO3 )
ii) metallic structures eg bridges , ships and
motor vehicles
-
7/24/2019 13B - Sulfur
12/17
Uses of SO2
1. Manufacture of H2SO4(Contact Process)
a. sulfur is burned in air S + O2 SO2 , H = exothermic
b. further oxidation :
2SO2 + O2
2SO3 ,
H = exothermic
-
7/24/2019 13B - Sulfur
13/17
Conditions :
catalyst
V2O5, vanadium (V) oxide 4500C , 1 - 2 atm
c. SO3absorbed in 98% H2SO4
SO3 (g) + H2SO4(l)
H2S2O7 oleum
H2S2O7 (l) + H2O (l) 2H2SO4(l)
-
7/24/2019 13B - Sulfur
14/17
Note : SO3is notabsorbed in water
Equation : SO3(g) + H2O (l) H2SO4(l) Reason :
Reaction is intensely exothermicas to
vaporise H2
SO4
formed(fumes are corrosive)
-
7/24/2019 13B - Sulfur
15/17
Industrial importance of H2SO4:
Manufacture of fertilisers , detergents ,pigments , synthetic fibres and organic
chemicals ( eg dyestuff and explosives )
-
7/24/2019 13B - Sulfur
16/17
2. As a preservative :
a. SO2is an inorganic food additive Eg : soft drinks . wine , soups , preserved
vegetables or fruits ( apricots , raisins )
Function of SO2
:
To kill or inhibit growth of yeast / fungi /
micro-organisms/bacteria
-
7/24/2019 13B - Sulfur
17/17
b. cooked and processed food contains carbonyl
compounds
SO2is a reducing agent( anti oxidant) thereforeretard oxidation of food
Eg : Prevents alcohols and carbonyl compound (
aldehydes ) in food from being oxidised and
forming sour-tasting acids
Note : SO32-(sulfites) are also used in food
preservation