7D Sulphuric Acid Flashcards
Discovery of Sulpuric Acid
Initially prepared by Distilling green vitriol
Sulphuric Acid was inititally called
Oil of Vitriol
Formula of Green Vitriol
FeSO4.7H2O
Why was it called oil of vitriol?
Prepared by distilling green vitriol
Occurence:
Free and Combined State
Free state of Sulphuric Acid:
Minute traces in hot springs
Near Sulphide beds. Ex: Hydrolysis of iron pyrites
Combined State:
Salts in minerals
Metallic Sulphates
4 General methods of preparation:
- By action of heat on nitric acid and sulphur
- By passage of chlorine through an aqueous solution of sulphur dioxide
- By dissolution of sulphur trioxide in water
- By hydrolysis of sulphuryl chloride
First Method
- Action of Heat on nitric acid and Sulphur
S + HNO3 —–> NO2 + H2O + H2SO4
(Conversion of Nitric acid to non-volatile sulphuric acid)
Second Method:
- By passage of chlorine through an aqueous solution of sulphur dioxide
Cl2 + SO2 + H2O —-> 2HCl + H2SO4
Third Method:
- By dissolution of sulphur trioxide in water
SO3 + H2O —–> H2SO4
Fourth Method:
- By hydrolysis of sulphuryl chloride
SO2Cl2 + 2H2O —-> H2SO4 + HCl
Manufucture of Sulphuric Acid is by
Contact Process
What are the parts of the unit in contact Process:
- Production of SO2
- Purification Unit
- Catalytic Oxidation
- Absortpion of SO3
- Dilution of Oleum
- Purification Unit contains:
- Dusting Tower
- Cooling Pipes
- Scrubbing tower
- Drying Tower
- Arsenic Purifier
- Testing Box
- Production of SO2 Contains:
- Blower
2. Sulphur or Pyrite Burners
- Catalytic Oxidation Contains:
- Contact Tower
- Absorption of SO3 Contain
Aabsorption Tower
- Dilution of Oleum Contains:
Dilution Tank
Use of
1. Production of SO2
A. Blower
For passage of purified air or Oxygen
Use of
1. Production of SO2
B. Sulphur or Pyrite Burners
For production of sulphur dioxide by burninng sulphite or iron pyrites
Use of
2. Purification Unit:
Purification of Gaseios mixture of SO2 and o2
Use of
2. Purification Unit:
C. Dusting tower:
For removal of dust particles by downward blow of steam
Use of
2. Purification Unit:
D. Cooling Pipes
For cooling of gases bby passage through isolated pipes
Use of
2. Purification Unit:
E. Scrubbing Tower:
For further removal of impurities and dust particles by downward sprpay of water
Use of
2. Purification Unit:
F. Drying tower:
For drying moist gases by downward spray of conc. H2SO4
Use of
2. Purification Unit:
G. Arsenic Puifier:
For removing arsenic oxide bby passage over ferric hydroxide
Use of
2. Purification Unit:
H. Testing box
For testing the purity of the gases by passage of light through a darkened box
Use:
3. Catalytic Oxidation:
I. Contact Tower
For Catalytic oxidation of - SO2 to SO3 By passage of sulphur dioxide and oxygen thrugh iron tower packed with vanadium pentoxide catalyst initially heated to 450
Use:
4. Absorption of SO3:
J. Absorption Tower:
For absorption of sulphur trioxide vapors by descending stream of con. H2SO4 (98%)
Use:
5. Dilution of Oleum
Dilution Tank:
For dilution of Oelum by flow of requisite amount of soft water
Reactions at Contact Process:
What are the 3 steps?
- Sulphur or Pyrite burners
- Contact Tower
- Absorption Tower
Reactions at Contact Process:
Step 1:
Chamber: Sulphur or Pyrite Burners
Conversion: Production of Sulphur dioxide by burning sulphur or iron pyrites [FeS2]
S + O2 —-> SO2
FeS2 + O2 —-> Fe2O3 + SO2
Reactions at Contact Process:
Step 2:
Chamber: Contact Tower
Conversion: Catalytic Oxidation of Sulphur Dioxide to Sulphur trionide
2SO2 + O2 —-> (V2O5, 450 to 500, 1 to 2 Atmos) SO3 + Heat
[Above equation for the catalysed reaction is exothermic, hence supplies energy]
Reactions at Contact Process:
Step 2:
Catalyst:
Vanadium Pentoxide
[V2O5]
[Pt]
Reactions at Contact Process:
Step 2:
Temperature:
450 to 500
Reactions at Contact Process:
Step 2:
Pressure:
1 to 2 atmospheres
Reactions at Contact Process:
Step 2:
Conversion Ratio:
98% of sulphur dioxide converted to sulphur Trioxide
Reactions at Contact Process:
Step 3:
Chamber: Absorption Tower
Conversion: Absorption of sulphur trioxide in 98% sulphuric acid to give oleum or pyrosulphuric acid [H2S2O7]
Reactions at Contact Process:
Dilution Tank:
Dilution of oleum with calculated amount of sodt water to give sulphuric acid of the desired concentration.
H2S2O7 + H2O —–> H2SO4
Contact Process:
1. Sulphur or Pyrite Burners
Sulphur Dioxide is obtained by burning sulphur or iron pyrites
Sulphur Dioxide is obtained by burning sulphur or iron pyrites
- When Sulphur is burnt in air, it burns with a pale blue flame forming sulphur dioxide and traces of sulphur trioxide
S + O2 —-> SO2
[S + O2 —-> SO3]
Why is burning Sulphur or iron pyrites in oxygen is preferred to purifies air?
Heat energy is wasted in heating the unreactive nitrogen component of the air
- Purification Unit:
The gaseous mixture of sulphur dioxide and oxygen [air] are passed through a purification unit before entering the contact tower
- Purification Unit:
Impurities present:
The gaseous mixture of SO2 and O2 contains impurities mainly dust particles or pyrites dust and arsenious oxide
- Purification Unit:
Reason For removal of Impurities:
The impurities if not removed tend to deactivate or posion the catalyst and thereby reduce it efficiency
- Purification Unit:
Method of removal of impurities:
The dust particles are removed in the dusting and scrubbing tower and the arsenious oxide {Passage over Fe(OH3)
Physical properties of Sulphuric acid
Color
Colorless
Physical properties of Sulphuric acid
Odour
Odourless
Physical properties of Sulphuric acid
Taste
Slight odour taste
Physical properties of Sulphuric acid
Nature
Dense,Oily, hygroscopic liquid
[Being hygroscopic it absorbs moisture from the atmosphere and hence is kept in airtight container
Physical properties of Sulphuric acid
Density
Heavier than water Pure acid (specific gravity1.85
Physical properties of Sulphuric acid
Solubility
Soluble in water in all proportions
Physical properties of Sulphuric acid
Constant boiling mixture
Forms a constant boiling mixture boiling at 338 degree celcius containing 98.5 percent of the acid
Physical properties of Sulphuric acid
Boiling point
338 degree celcius
[B.P. of liquid HCl is -83 degree celcius and dilute Nitric acid is 86 degree celcius}
Physical properties of Sulphuric acid
Melting point
Freezes to colorless crystals having m.p. 10.4 degree celcius
Physical properties of Sulphuric acid
Conductivity
Pure acid:Almost a non-conductor of electricity
Dilute acid:Good conductor of electricity
