7C Nitric Acid Flashcards
Nitric acid was Initially called
Aqua Fortis
Nitric Acid Occurs in
Free and Combined state
Free State
During lightnings, atmospheric nitrogen is oxidised to Nitroc oxide
Nitric oxide is further oxidised to nitrous oxide.
NO2 combines with H2O to form nitric acid
Then combines with metallic carbonates to form Nitrates
Fixation of atmospheric nitrogen
Fixation of Free atmospheric nitrogen into uself nitrogenous compounds in the soil
Combined State:
Chile Salt Petre
Bengal Salt petre or Nitre
Laboratory Method:
From potassium or sodium Nitrate
and Conc. H2SO4
Equation:
KNO3 + H2SO4 —> (<200) KHSO4 +HNO3
Laboratory Method:
Reactants:
KNO3
Conc. H2SO4
in glass retort
Laboratory Method:
Products:
Potassium Bisulphate
Nitric acid Vapours
Laboratory Method:
Condition:
Temperature of reactants less than 200
Laboratory Method:
Procedure:
A mixturfe of equal parts by weright of sodium nitrateand conc. h2so4 are gently heated in glasss retort
Laboratory Method:
Observation:
On heating the misture in glass retort
The volatil nitric acid is displaced
The vapours are collected in receiver
Cooled from outside with cold water
Laboratory Method:
Collection:
Collected in water cooled Reservior
Laboratory Method:
Precaution:
Complete apparatus made of glass
HCl is not used
Temperature is maintained and controlled
Laboratory Method:
Identification:
Heating alone or with copper turining –> Reddish brown fumes of NO2
NO2 -> FeSO4 (acidified) —> Brown
Laboratory Method:
Why is H2SO4 used?
Strong non-volatile acid
Displaces more volatile nitric acid from its salt
Laboratory Method:
Why is HCl not used?
Being volatile it is not uswd to displace another volatile aCID
Laboratory Method:
Molar ratio of reactants:
1:1
Half of the hydrogen of the acid is used up.
Laboratory Method:
Apparatus:
An all glass apparatus
Consists of:
1. Glass retort —> Reactants are heated
2. Water cooled reservior –> Collect condensed vapours of Nitric acid
Laboratory Method:
Why glass?
Nitric acid is corrosive
Attacks Rubber, Cork etc.
Laboratory Method:
Temperature of the reaction:
<200
Laboratory Method:
High temperature:
- Damage to glass
- Further decomp. of Nitric acid
- Formation of a hard residual crust of the corresponding sulphate.
Poor conductor of heat, Sticks to the surface of the glass and cant be removed easily
Why is Nitric acid obtained in laboratory Yellowish Brown
Decomposition of Nitric acid, Results in Formation of Reddish Brown Nitrogen Dioxide which remains dissolved in the acid, thereby imparting color to it
HNO3 —>
NO2 + H2O + O2
Yellow brown tinge can be remofved by:
- Bubbling of air or carbon dioxide
2. Dilution with water
Bubbling of air or carbon dioxide:
Drives out the NO2 gas from the warm acid
Further oxidises NO2 to Nitric acid
- Dilution with water:
Causes dissolution of NO2 gas which is soluble in water
Manifucture of Nitric acid is by
Ostwald’s Process
3 Steps In ostwald’s Process:
- Catalytic chamber
- Oxidation chamber
- Absorption tower
- Catalytic chamber:
Conversion:
Catalytic oxidation of ammonia to nitric oxide
- Catalytic chamber:
Reaction:L
NH3 + O2 —> (Pt, 700 to 800) NO + H2O + 21.5 Kcals
- Catalytic chamber:
Reactants:
a. Pure dry Ammonia
b. Dry air
- Catalytic chamber:
Ratio of Reactants:
Ammonia : Air
1:10 by volume
- Catalytic chamber:
Catalyst:
Platinum Gauze
- Catalytic chamber:
Temperature
700 to 800 (Maintained electrically)
- Catalytic chamber:
Nature of Reaction:
Exothermic
- Catalytic chamber:
Products:
- NO
2. Steam
- Catalytic chamber:
Conversion ratio:
95% of NH3 to NO
Rest burnt to N2 and Steam
- Oxidation Chamber:
Conversion:
Oxidation of NO to NO2
- Oxidation Chamber:
Reaction:
NO + O2 –> (50) NO2
- Oxidation Chamber:
Temperature:
50
- Absorption Tower:
COnversion:
NO2 to HNO3 by absorption in water in the presence of excess air
- Absorption Tower:
Equation:
NO2 + H2O + O2 —> HNO3
- Absorption Tower:
Temperature:
Ordinary Temperature
- Absorption Tower:
Product:
Nitric Acid
Nitric acid on skin
Extremely Corrosive action —> Painful blisters
Protein of the skin forming a yellow compound, Xanthoproteic Acid and hence stains the skin yellow
Why sistillation or boiling cant be used to concentrate nitric acid beyond certain concentration?
An aqueous solution of nitric acid forms
A constant boiling misture at 121, 68% acid.
What is Constant Boiling Mixture?
Is the one which bouils without the change in composition
Hence on boiling the above misture, Evolves out vapourws of both acid and water in the same proportion as in the liquid
Further concentration:
Distillation of the acid under reduced pressure in the presence of concentrated sulphuric acid. 98%