Laborotory Preparation of Chlorine by the application of heat and Without the application of heat Chemistry-II (CTEVT)

 Laborotory Preparation of Chlorine by the application of heat and Without the - application of heat  Chemistry-II (CTEVT) 

Halogens:

Chlorine 

Symbol: cl

Atomic Number:17

Atomic Mass: 35

Occurrance:

They are very active non-metals and are always obtained in combined state mostly as salt of alkali and alkaline earth metals. These salts are highly soluble in water and they occur in ocean water, sea water contain 2% chlorine as chloride.

. Laborotory preparation of Chlorine

1.) By the application of heat:

Chlorine is prepared in the laboratory by heating the mixture of sodium or Potassium Chloride Conc H₂SO₄ and MNO₂  the HCL first formed is oxidised by  MNO₂  with  the evolution of chlorine gas. Chlorine is heavier than air ( Vapour density 35.46) therefore it is collected by the upward displacement of air.

Nacl + conc.H₂SO₄  ͢Δ  NaH₂SO₄ + HCl] ×2
MNO₂ + H₂SO₄ →  MNO₂ + H₂O +[O]
2Hcl    + [O]  → Cl₂  +H₂O

---

2Nacl + 3H₂SO₄ + MNO₂  ͢Δ 2NaH₂SO₄ + MnSO₄ +2H₂O + Cl₂    

Purification:

The impurities in the chlorine thus prepared are HCL and water. HCL is remov ed from Cl₂  by passing the gas through water in a wish-bottle because HCL is highly Soiuble in water whereas Cl₂  has very low solubility and it gets saturated readily and escaped from the wash bottle as moist Cl₂  then the moist gas is allowed to pass from the delivery tube through another wash bottle containing conc.H₂SO₄ where moisture is absorbed completely finally dry  Cl₂  is collected in the gas jar by the upward displacement of air.

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2.) Without the application of  Heat:

Principle

when crystals of KMNO₄  are treated with conc HCL evolution of Cl₂  gas takes place at ordinary temperature without the application of heat.

2 KMNO₄  + 6 Hcl  → 2 Kcl + 2 Mn Cl₂  +3H₂O +5[O]
 2 HCl +[O] → H₂O +Cl₂  ] 5  

---

2 KMNO₄  + 16 HCl →  2 KCl + 2 Mn Cl₂  +8 H₂O +5 Cl₂ 

This is very convenient laboratory method because it takes place in cold and the rate of production of chlorine can easily be controlled and if the gas is collected over brine the experiment need not be conducted in a fume chamber.

A brisk reaction occurs as conc HCl is dropped into the flask containing KMNO₄ . The gas free from Hcl and moisture can be collected in the gas jarif the process of purification is done as mentioned in case a.

Properties and Uses of Chlorine:

1.) Chlorine displaces Br₂  and I₂  from bromide and iodide solution

Cl₂  + 2Na Br  →  2Nacl +Br
Cl₂  + 2NaI   →  2Nacl + l₂   

2.) Action with Water  

It dec omposes water whn exposed to sunlight to liberate Oxygen.

Cl₂  + 2H₂O  → 4HCl + O₂  

3.) Bleaching Action

Declorication of a substance by a reagent is termed as bleaching action. Chlorine is suitable bleaching agent. Its bleaching action is permanent.

Cl₂  + H₂O → HCl + HOCl 
  HOCl  → HCl +[O]
Colored Flower + [O]  → Colorless Flower

4.) Action with Hypo [ Sodium thio Sulphate (Na₂  S₂  O ₃  )]

 Na₂  S₂  O ₃ + Cl₂  + H₂O  →  Na₂  SO₄  +2HCl +S 

                                                 Sodium Sulphate

5.) Action With dry Slaked Lime

Chlorine reacts With dry Slaked to give Bleaching Powder.

Ca (OH) ₂  + Cl ₂  →  CaOCl₂  + H₂O 

                                     Bleaching Powder

Use of Chlorine

1. It is used to remove the colcuring Matter.

2. Use as a Disintectant and Germicide for the sterilization of Drinking water.

3. Using the Manufacture of DDT ( dichlore diphenyi trichloro etane) and Preparation of bleaching Powder Chlorform , Carbon tetra Chloride (CCL4)