Detection of nitrogen in organic compond | Chemistry HSEB notes XI

Sodium extract solution is prepared and 1ml of that Na extract solution is taken in a clean test-tube and added few drops of sodium hydroxide solution if sodium extract solution is not Alkaline. To this solution 1ml of freshly prepared ferrous sulphate is added. Whole solution is then heated to boiling for few minutes. The solution is then cooled under tap . To this cooled solution 8-10 drops of concentrated hydrochloric acid is added and 1 drop of ferric chlorite solution is added. After this, apperance of Prussian  blue or green precipitation of ferric ferrocynate conforms the presence of Nitrogen in given organic compound.

Reaction involved :

1.     Organic compound containing Nitrogen during sodium fusion give NaCN which is water soluble ionic salt so sodium extract solution contain NaCN.

    

          Na + C + N ----------------> NaCN

    

     2.     Excess of sodium if remained reacts with water to give NaOH.

      

          Na + H2O ------------------> NaOH + H2

     3. This sodium hydroxide solution and added NaOH reacts with ferrous sulphate to      give ferrous hydroxide which has dirty green colour.

          FeSo4 + 2NaOH ----------------> Fe(OH)2 + Na2So4 (dirty green ppt)

     4. Ferrous hydroxide then reacts with NaCN to give sodium ferrocyanide.

          Fe(OH)2 + 6NaCN ----------------> Na4[Fe(CN)6] + NaOH (sodium ferrocyanide)

5. Sodium ferrocyanide then reacts with ferric chloride solution to give ferric ferrocyanide which has prussion blue or green colour which comforms the presence of Nitrogen.

3Na4[Fe(CN)6] + 4FeCl3 ---------------> Fe4[Fe(CN)6]3 (ferric cyanide) + 12NaCl

(if the product formed upon reacting with conc HCl gives Prussian blue or green colour 

then we can comform the presence of Nitrogen in given organic compound)

Sometimes during Nitrogen test there is the formation of blood red colour which shows the presence of both Nitrogen and sulphur in given organic compound. If the organic compound contains N as well as S during sodium fusion there will be the formation of NaCN instead NaCN which directly reacts with feric chloride solution to give ferric thio cynite which has blood red colour.

Na + S + C + N ---------------> NaCN (Sodium thio cyanide)

NaCN + FeCl3 ----------------> Fe(CNS)3 (ferric sulphocyanide, blood red)

Manufacture of Ammonia by Haber's process | HSEB Chemistry notes

More on original site : Manufacture of Ammonia by Haber's process

Principle :  In this process , Ammonia is prepared from nitrogen and hydrogen. In ordinary condition , nitrogen do not react with hydrogen but when it is mixed with hydrogen in the ration 1:3 under 450 C temperature and 200-500 atm pressure in presence of Iron as catalyst and Molybdenum as promoter then it combines to form

Ammonia (NH3).

The reaction is exothermic, reversible and proceeding with decrease in volume. So, following condition is needed for better yield of it :

a. Low temperature : The reaction is exothermic , it as a rule is followed by low temperature. But if the temperature is very low then the rate of reaction will

be very slow and production of Ammonia will not be economically fruitful and beneficial. So optimum temperature of 450 C is maintained in this process.

b. high pressure : The reaction is reversible so it favored by high pressure. So pressure of about 200-500 atm is maintained.

c. High concentration : If the reactant are excess the the product formed will also be same . So either hydrogen or nitrogen in the reactant side is made excess to 

produce high amount of ammonia.

d. Use of catalyst : In absence of catalyst, the reaction will be slow. So, Iron is used as catalyst along with molybdenum as promoter to increase the rate of reaction

without hampering it. 

Process : In this process, N2 is treated with H2 in the ratio 1:3 . Then the gaseous mixture is passed through compressor in which pressure of 200-500 atm is applied.

Then the gases mixture is passed through catalyst chamber packed with finely divided Iron + molybdenum. The chamber is initially heated to about 450 C to initiate the 

reaction. During this condition , 15% of the gaseous mixture is turned into ammonia. Thus , the gaseous coming out of the chamber contains NH3 and unreacted H2 and N2. These are then passed through condenser to condense only ammonia not H2 and N2. The liquefied ammonia is collected at the bottom from time to time. The other uncombined 

H2 and N2 is recycled and reprocedded. 

Chemistry HSEB notes | Labarotory preparation of hydrogen sulphide

Hydrogen sulphide gas can be prepared in the laboratory in following ways :

Theory : Hydrogen sulphide gas can be prepared in the laboratory by reacting iron sulphide (FeS) with dilute non-oxidizing acid like HCl and H ₂ SO ₄ .

Reaction : FeS + dil H ₂ SO ₄ ---------- > H ₂ S + FeSO ₄

                 FeS + HCl ----------- > H2S + FeCl2

Some iron sulphide in kept in the Wolfe's bottle which is fitted with delivery tube and thistle funnel. The other end of delivery tube is introduced to an erect gas jar for the collection of H ₂ S gas by upward displacement of air.

Dil acid is introduced to Wolfe's bottle through thistle funnel. Now the acid comes in contact with the FeS and H ₂ S gas is produced which is collected in the gas jar.

Purification : The H ₂ S gas produced in the laboratory may be contaminated with hydrogen gas or some acid spray. Thus, H ₂ S is purified by passing the mixture of gas through aqueous suspension of Magnesia (MgO) . MgO absorbs H ₂ S to for magnesium hydrosulphite , Mg(H ₂ S) leaving behind hydrogen gas. When this Mg(H2S) is heated at the temperature of about 60-70 C, purified H ₂ S gas is produced.

MgO + H ₂ S ---------- > Mg(H ₂ S) ₂ + H ₂ O
Mg(H ₂ S) ₂ ----------- > H ₂ S + MgS

Chemistry HSEB note | Kipps apparatus

HSEB Chemistry XI (Laboratory methods and Kipp's apparatus)

Hydrogen Sulfide is needed frequently in laboratory but intermittently for precipitation of basic radical which is done with the help of Kipp's apparatus

kipps apparatus

As shown in figure, upper bulb A has tappering end which reach to the bottom of bulb C. Bulb B is interconnected with bulb C. It has an outlet with a tap which can be opened and closed. Some iron sulfide is kept in the bulb B. Dil acid is passed in the  funnel which reach to the bottom of bulb C and again raises up to meet with iron sulfide. When the acid and FeS, H ₂ S gas is produced which can be collected by open which opeing the tap.

When H ₂ S gas is not needed , the tap is closed. The gas continues  in bulb b as tap is closed. The pressure of gas increases which pushes the acid from bulb b to bulb c which again returns back to the bulb A. Now the acid is not in contact with FeS so H ₂ S gas will not be produced.

                                               When tap is opened, reverse phenomenon occurs.

Chemistry HSEB notes | Laboratory preparation of sulfur dioxide gas

Sulfur dioxide gas (SO2) is prepared in the laboratory in following ways :

Theory : Sulfur dioxide gas is prepared in the laboratory by heating copper turnings with conc Sulfuric acid (H₂SO₄) .

Reaction involved :

Cu + conc H₂SO₄ ----------- > CuSO₄ + SO₂ + H₂O

 H₂SO₄ ---------- >SO₂ + H₂O + [  O ]
 Cu + [  O ] ---------- > CuO
 CuO + H₂SO₄ ---------- > CuSO₄ + H₂O

Cu + conc 2 H2SO4 ----------- > CuSO4 + 2 H2O +SO2

Laboratory preparation of sulfur dioxide gas

Procedure :

As shown in the figure, some copper turnings are kept in the round bottom flask which is fitted with thistle funnel and delivery tube.

The other end of delivery tube is kept in a absorption bottle containing conc sulfuric acid. Conc Sulfuric acid is poured in the thistle funnel which reaches to the round bottom flask to start the reaction. Again , one end of delivery tube is kept in absorption bottle and other end is introduced to an erect gas jar for the collection of sulfur dioxide gas by upward displacement of air.

The copper or flask is heated. On doing so the reaction between acid and cupper takes places and sulfur dioxide gas (SO₂) is produce in the flask. The SO₂ gas produced is not  pure so it passed through absorbtion bottle containing con H₂SO₄ to remove moisture from the gas as H₂SO₄ is a great dehydrating agent. After removement of moisture finally, SO₂ gas is collected in the gas jar by upward displacement of air.

Test :

The presence SO₂ gas can be tested by introducing potassium manganese to the mouth of the jar. If it discolourizes then we can know that SO₂ is collected in the jar.

HSEB notes | Sulphuric acid as a dehydrating agent, an oxidant and an acid

i. Sulphuric acid as a dehydrating agent :

H2SO4 has a great affinity for water, with water it forms a hydrate with evolution of high heat.

H2SO4 + H2O ----------> H2SO4 + H2O + Heat

Example showing sulphuric acid as a strong dehydrating agent are as follows :

1. Charring of sugar : It removes water molecule from sugar or sucrose and chars it with production of black carbon mass.

C12H22O11 + H2SO4 ---------- > 12 C (black mass)  + 11 H2O

2. It remove water of crystallization from blue cuppor sulphate crystals and turn it into white.
CuSO4 . 10 H2O (blue)+ H2SO4 ---------- > CuSO4 . H2O (white) + H2SO4. 4 H2O

3. It remove water from oxalic , formic acid and etyl alchohol :

With formic acid :

HCOOH + H2SO4 ---------- > CO + H2O

With oxalic acid :

(COOH)2 + H2SO4 ---------- > CO + CO2 + H2O

With ethyl alchohol :

C2H5OH + H2SO4 ---------- > C2H4 + H2O

ii. H2SO4 as an oxidizing agent :

1. With non-metals : Hot and conc H2SO4 can oxidize non-metals like carbon, sulphur and phosphorous.

With carbon :
H2SO4 ---------- > SO2 + H2O + [ O ]
C + [ O ] ------------ > CO2

With phosphorous :

P4 + 10 H2SO4 ----------- > 4 H3PO4 + 10 SO2 + 4 H2O

With sulphur 
:
S + H2SO4 ----------- > SO2 + H2O

2. With bromides and iodides : Conc and hot H2SO4 can oxidize bromides (HBR , KBR) and iodides (KI, HI) to free bromine and iodine respectively.

HBR - H2SO4 ----------- > SO2 + H2O + BR2
HI + H2SO4 ------------ > SO2 + H2O + I2

Determination of equivalent weight of a metal by hydrogen diplacement method

(science Notes for HSEB Grade 11and 12 students for botany chemistry physics and zoology)

Theory : This method can be used to determine the equivalent weight of a metal which can evolve hydrogen gas with dil mineral acid like HCl , H2SO4. Some metals like Zn, Mg etc which lie above hydrogen in the electrochemical series can evolve hydrogen gas.
In this process, first definite weight of metal is taken and treated with excess of dil mineral acid. Due to this hydrogen gas is produced. The volume of gas obtained is at the lab condition of temperature and pressure so it is converted to volume at NTP by combined gas equation  i.e P1 V1/T1= P2 V2/T2.
After it is converted to volume at NTP it is then converted to mass using mole concept or following formula :
Mass of hydrogen = Volume of hydrogen at NTP (in ml) . 0.000089
From the mass of hydrogen the equvalent weight of metal can be obtained by following formula :
Equivalent weight of metal = (mass of metal / mass of hydrogen ) . 1.008

Procedure : A peice of metal is taken and it's weight is measured by using chemical balance. Then it is converted to "V" shaped so that it sinks in water and it is tied with a thread and kept in a large beaker filled with water. A small short funnel is inverted over the metal inside the beaker in such a way that the steam of the funnel is completly inside the water. An eudiometric tube is taken and it is filled half with acid and remaining half with water. Then it is inverted over the funnel such that there is no bubble left in the tube and it is clamped with a stam. The acid inside the tube comes down slowly and reacts with the metal and hydrogen gas is evolved which is collectef in the eudiometric tube above the water. The apparatus is left for the completion if the reaction. In the meanwhile the temperature and pressure of the lab is noted. After the completion if the reaction i.e when hydrogen gas stops producing, the tube is shaken for a while to collect all the bubble of hydrogen gas into the tube. Then the tube is taken out of the beaker, closing the mouth of the tube carefully and the volume of hydrogen is is noted by kepping the tube inside the water in a tall jar. The level of water inside and outside the tube is made equal so that the pressure inside and outside becomes same. Then is volume of hydrogen at lab condition of temperature and pressure is converted to volume at NTP and to mass. From the mass of the hydrogen , the equivalent weight of the metal can be determined.

Manufacture and condition required for better production sulphuric acid

Condition required for better production sulphuric acid.

The above reaction is exothermic and proceeding with decrease in volume as 3 molecule on
reactant is producing only two molecules of product. Sulphur dioxide is oxidized to
Sulphur trioxide and it may decomposed back to Sulphur dioxide. According to Le-Chatelier
the following condition should be maintained :

1. Excess use of air or oxygen and Sulphur dioxide :

Air or oxygen should be used in excess amount along with Sulphur dioxide for greater
production of Sulphur trioxide.

2. Temperature 

The reaction is exothermic. According to Le-chatelier principle low temperature is needed
to carry the reaction in forward direction. But if the temperature is very low then
the the rate of reaction will be slow and will not be productively advance. So, premature
of 400-450 C is maintained to proceed in forward direction and
without hampering the reaction.

3. Pressure :

The reaction is reversible and proceeding with decrease in volume. According to Le-chatelier priciple
high pressure is needed for this type of reaction but if the pressure is high then
the acid proof walls on the industry may burst due thigh pressure. Thus pressure of
2-3 is maintained.

4. Use of Catalyst

Looking at temperature and pressure the reaction may be slow so catalyst is used in the
reaction. Catalyst like divanadium pentaokide(V2O5) or platinum asbestos is used.
Platinum albestos is not used because is not cheap and is easily poisoned by arsenic
impurities mostly present in so2. Instead divanadium pentaoxide is used as it is cheap and doesn't poison.

5. Purity of Gases

All the gases used in the reaction should be in completely dry and pure state as any impurities present in the reacting gases act as catalytic poision and reduce the efficiency of catalyst.

Properties and uses of Sulphur dioxide gas (SO2)

Physical Properties

1. They are colourless, poisionous and corrosive gas having pungent ordour. They are
nasal throat and lungs irritant.
2. They are higly soulble in water. They dissolve to form sulphorus acid and they are heavier than air.
3. They liquidify at -10 C to form colourless liquid and solidifies at 76 C.

Chemical properties

1. Acidic nature :

                    Sulphur dioxide gas is an acid anhydride of Sulphurous gas, it dissovles to form Sulphurous  gas which is a weak diprotic acid.

H ₂SO₃ --------------> H₃ O^- + HSO₃ ^-

HSO ₃ --------------> H ₃^-O + SO ₃^--

When such type of diprotic acid reactes with base it undergoes nutralization reaction in two ways forming neutral and acidic salt.

H₂ SO ₃ + NaOH --------------> H ₂O + Na₂ SO₃ (Acidic salt)

H₂ SO ₃ + NaOH --------------> H₂ O + NaSO ₃   (Neutral salt)

2. Sulphur dioxide as reducing agent :

It is strong reducing agent.

a. It reduces halogens to haloacids.

Cl + H₂ O --------------> HCl + [O]

[O] + SO ₂ + H ₂O --------------> H₂ SO ₄

--------------------------------------------------

Cl+ H ₂O + SO₂ --------------> HCL + H ₂SO ₄

b. It reduces Ferric salt to ferrous salt.

SO₂  + H ₂O --------------> H ₂SO₄  + [H]

[H] + Fe₂ (SO4)₃ --------------> FeSO₄ + H₂ SO ₄ 

HSEB chemistry notes | Allotropes of Sulphur

Allotropes of Sulphur

1. Rhombic or Quadrahederal Sulphur

It is the most stable allotrope of Sulhphur. The element Sulphur exist in nature
in this Rhobic variety. All the other allotrope of sulphur can be converted to
this rhombic sulphur at ordinary room temperature but rhombic sulphur cannot be
converted to other form at room temperature.It is not conductor of heat and
electricity. It is not solube in polar solvent like water and soluble in carbon
disulphite , chloroform etc.It 's melting point is 114.5 C, boiling point is 445 C
and specific gravity is 2.06. It is transparent crystalline having pale yellow colour.

Preparation : When rool of sulphur is treated with carbon disulphite it dissolves, and
the solution thus obtained is transferred in a flat evaporating dish. Carbondisulphite
slowly escapes out as it is a volatile compound leaving behind crystals of sulphur known as
Rhombic sulphur.

2. Monoclinic or Prismatic Sulphur

It is crystalline form of sulphur consisting of S8 atom and the molecule in this type
of sulphur is compactly packed with each other to give needle like crystal lattice.
It has amber colour. It's specific gravity is 1.96, boling point is 440 C and melting point is 119 C. It is bad conductor
of heat and electricity. It is insolube in water and soluble in CS2. It is stable only
above 96 C and slowly converts into rhombic variety at room temperature.

Preparation : It is obtained by melting roll of sulphur and cooling it under a crust
is formed. Few holes are made on the crust and mother luquior is poured from it and
air is passed inside it through the hole. As a result Monoclinic sulphur is obtained.

3. Plastic Sulphur

It is amorphous form of sulphur.When roll of sulphur of sulphur in powder form is
heated abour 160 C in a hard glass TestTube it melts to form dark brown vicsious liquid.\
The hot soultion thus obtained is poured in a cold water in a beaker so that it solidifies
to form dark solid of sulphur havinf elastisity.This is called as plastic sulphur.

It has amber colour. It is non-conductor of heat and electricity. It is insoulbe both
in water and CS2. It's specific gravity is 1.95 and it has no sharp melting point as
it is supercooled solid.Since it is in amorphous form it has no fixed shape but it is
supposed to be remained in long zigzag shape by opening all the 8 atom of sulphur.

4. Milk of Sulphur

When roll of sulphur is treated with Calcium hydrooxide (Ca(OH) 2) it forms Calcium pentaoxide and Calcium thiosulpide and the brown solution thus obtained is filtrated and filtrate solution
is treated with conc Hydrochloric acid to form white colour precipitation of sulphur
know as milk of sulphur.

It is opaque, white solid. It is Insoulbe in water and solube in CS2.At ordinary temperature it also
slowly coverts into Rhombic variety.

HSEB notes | Formula and name of some Common Compounds

Formula and name of some Common Compounds

v1. Bleaching Powder                                         - CaOCl₂

2. Sal ammoniac                                         -  NH ₄ Cl

3. Quick lime                                                    - CaO

4. Slaked lime                                                   - Ca(OH) ₂

5. Hypo                                                             - Na₂ S₂ O₃ 5H ₂O

6. Laughing gas                                                - N ₂ O

7. Baking soda                                                  - NaHCO₃

_8. Galena (Lead (II) sulfide)                              -  PbS

9. Limestone                                                      - CaCO₃

_10. Oil of vitriol (Sulfuric acid)                         - H₂SO₄

_11. Salt (Sodium chloride)                                 - NaCl

12. Washing soda                                              - Na₂CO₃^.10 H₂O

13. Quicksilver (mercury)                                  -  Hg

14. Plaster of Paris                                            - CaSO₄^. H₂O
15. Caustic potash                                            - KOH
16. Soda ash                                                     - Na2CO3
17. Baking Soda                                               - NaHCO ₃
18. Sulphurated Hydrogen                               - H ₂ S
19. Marsh gas                                                   - CH4
20. Horn Silver                                                 - AgCl
21. Carbide                                                       - CaC ₂
22. Hydroiodic acid( Hydrogen Iodine)           -  HI
23. Acetate                                                        - CH ₃ COO-
24. Bicarbonate                                                 - HCO ₃ -
25. Hypochlorite                                                - ClO-
26. Gypsum                                                        - CaSO ₄ . 2H 2O

27. Green Vitriol                                                - FeSO ₄ . 7H ₂O
28. Blue Vitriol                                                  - CuSO4 . 5H2O

29. White Vitriol                                                - ZnSO ₄ . 7H ₂O

30. Vinegar Acetic Acid                                     - CH ₃COOH

31. Lunar Caustic                                              - AgNO3

32. Chloroform (Tricholoro Methane)              - CHCl ₃

33. Borax                                                           - Na ₂ B ₄ O ₇ . 10H ₂ O34

35. Sugar Sucrose                                             - C₁₂ H ₂₂ O ₁₁
36. Heavy Water Duterium Oxide                     - D ₂O
37.Globar's Salt                                                 - Na2SO2 . 10H2O
38. Calomel                                                       - HgCl

39. Sand                                                            - SiO ₂
40. Alcohol (Ethyl Alcohol)                                - C ₂H ₅ OH