BLEACHING POWDER

BLEACHING POWDER
Chemical name : Calcium chloro hypo chloride. Commercial name : Bleaching powder. Chemical formula : Ca(OCl)Cl.H2O or CaOCl2.H2O.
It is a dirty white amorphous powder with pungent smell of chlorine gas.
Industrial Preparation of Bleaching Powder
On industrial scale it is prepared by "Hasen-Clever Method".
Raw Material
1. Slaked lime Ca(OH)2 2. Chlorine gas
Hasen-Clever Plant
The plant consists of four cylinder of cast-iron. Each cylinder is about 2 to 3m long .Each cylinder is provided with a stirrer to ensure the mixing of substances. There is an inlet in the upper most cylinder for Ca(OH)2. The bottom cylinder has an inlet for Cl2 and outlet for bleaching powder. Each cylinder is connected to the other by means of pipes.
Procedure
Slaked lime is introduced in the first cylinder with the help of compressed air .Cl2 gas is introduced from the lower most cylinder .In this way these two substances meet, when proper saturation is reached, the product is separated from the last cylinder as bleaching powder.
Ca(OH)2 + Cl2 è Ca(OCl)Cl.H2O
Properties
It is a strong bleaching agent. Due to liberation of chlorine gas in aqueous solution it decolorize different fabrics. It is also an antiseptic.
Reaction with water: Ca(OC)Cl + H2O è Ca(OH)2 + Cl2 With HCl: Ca(OCl)Cl + 2HCl è CaCl2 + Cl2 + H2O With CO2: 2Ca(OCl)Cl + CO2 + H2O è CaCO3 + CaCl2 +2HOCl
Uses
As oxidizing and bleaching agent it is used in textile and other industries. It is also used in the purification of drinking water.
Q: How would convert magnesite in to Mg(OH)2 ? Ans: Chemically magnesite is magnesium carbonate (MgCO3). First magnesite is heated, on heating it decomposes to MgO. MgCO3 è MgO + CO2 MgO is heated with carbon and chlorine to produce MgCl2. MgO + Cl2 + C è MgCl2 + CO Finally MgCl2 is treated with Ca(OH)2 to produce Mg(OH)2. MgCl2 + Ca(OH)2 è Mg(OH)2 + CaCl2

PLASTER OF PARIS EPSOM SALT

Q: What is plaster of Paris? How is it prepared?
Ans: Calcium sulphate hemi hydrated is commonly known as "plaster of Paris". Chemical formula: CaSO4.1/2H2O Plaster of Paris is prepared by gypsum.
Preparation
When gypsum is heated up to 1000C ,it loses some molecules of water of crystallization and forms an amorphous white solid known as plaster of Paris.
CaSO4.2H2O è CaSO4.1/2H2O+ 3/2H2O
Properties
Plaster of Paris when mixed with water sets within few minutes. The setting of plaster of Paris takes place with expansion and its surface becomes very smooth .Due to this property plaster of Paris is used in moulds.
Question: What is Epsom salt? How is it prepared.
Magnesium sulphate hepta hydrated is commonly known as "Epsom salt". Chemical formula: MgSO4.7H2O
Properties & uses
It is a semi transparent white crystalline solid. It is soluble in water. It is used as purgative in medicines. It is used in Paper, soap and ceramics industry .
Methods of preparation
Epsom can be prepared by treating suitable substance with Sulphuric acid From Mg:
Mg + H2SO4 è MgSO4 + H2
From MgCO3 :
MgCO3 when treated with H2SO4. MgSO4 is obtained.
MgCO3 + H2SO4 è MgSO4 + H2O + CO2
From Mg(OH)2:
Mg(OH)2 + H2SO4 è MgSO4 + 2H2O
From MgO :
MgO + H2SO4 è MgSO4 + H2O
Effect of Heat
When Epsom is heated, it loses water of crystallization to form anhydrous magnesium sulphate.
MgSO4.7H2O è MgSO4 + 7H2O

CHEMISTRY OF SODIUM HYDROXIDE

CHEMISTRY OF SODIUM HYDROXIDE
Commercial name : caustic soda
On industrial scale sodium hydroxide can be prepared by the following methods. 1) Castner - Kellner Process. 2) Gibb's Method. 3) Nelson's Method.
Castner - Kellener Process
Principle
In castner-kellner method NaOH is prepared by the electrolysis of aqueous solution of NaCl(Brine).
Concentration of brine
25 % mass/mass i.e. 25 gm of NaCl is dissolved in 75 gm of water.
Castner-kellner cell
It is a rectangular tank of steel. Inside of tank is lined with "ebonite". Anode is made of titanium. Flowing layer of mercury (Hg) at the bottom of tank serves as cathode.
Details of process
Ionization of NaCl 2NaCl è 2Na+ + 2Cl-
When electric current is passed through brine, +ve and -ve ions migrate towards their respective electrodes. Na+ions are discharged at mercury cathode. The sodium deposited at mercury forms SODIUM AMALGAM. Chlorine produced at the anode is removed from the top of the cell.
Reaction at cathode
2Na+ +2 e- è 2Na
Na forms amalgam.
Na + Hg è Na/Hg
Na+ ions are discharged in preference to H+ ions due to high over voltage. Na+/Na: E.P. = -2.71 volt H+/H : E.P. = 0.00 volt
Reaction at anode
2Cl- è Cl2 + 2e-
Formation of NaOH
Amalgam moves to another chamber called "denuder", where it is treated with water to produce NaOH which is in liquid state. Solid NaOH is obtained by the evaporation of this solution.
2Na/Hg + 2H2O è 2NaOH + H2 + 2Hg
Advantages of castner's process
NaOH obtained is highly pure. The process is very efficient. Possible reaction between NaOH and Cl2 is avoided as NaOH is obtained in a separated chamber.
Disadvantages
High electricity consumption. Environmental pollution due to escape of Hg vapours.

CHEMISTRY OF SODIUM CARBONATE ( Na2 CO3 ) SODA ASH

CHEMISTRY OF SODIUM CARBONATE ( Na2CO3 )
Soda Ash
INDUSTRIAL PREPARATION OF SODIUM CARBONATE
On industrial scale sodium carbonate is prepared by Ammonia Solvay Process.
Raw Materials
1. Sodium Chloride 2. Lime Stone (CaCO3) 3. Ammonia
Details of the process
At first stage a saturated solution of sodium chloride is prepared which is also known "BRINE". Composition of solution of NaCl (brine) is 28% m/m.
Steps of preparation
Ammoniation of Brine
In this stage saturated brine is allowed to flow down an ammoniating tower. This tower is fitted with mushroom shaped baffles. These baffles control the flow of brine and ensure the proper mixing and saturation of ammonia.
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Carbonation of ammoniated brine
In the second step, ammoniated brine is allowed to trickle down a carbonating tower known as solvay tower. This tower is also fitted with baffle plates. Here brine is mixed with carbon dioxide gas, produced by heating lime stone in a separate chamber called "kiln".
CaCO3 èCaO + CO2
the baffle plates ensure the flow of solution and breaks up carbon dioxide into small bubbles to produce good conditions for reaction.
Flow Chart
Chemistry of Solvay tower
CO2 reacts with ammonia to form ammonium carbonate.
2NH3 + CO2 + H2O è(NH4)2CO3
Ammonium carbonate further reacts with CO2 to form ammonium bicarbonate.
(NH4)2CO3 + CO2 + H2O è2NH4HCO3 (aq.)
Ammonium bicarbonate then react with NaCl to form sodium bicarbonate.
NH4HCO3 + NaCl èNaHCO3 + NH4Cl
Due to exothermic nature of above reactions, solubility of NaHCO3 increases. To counter this effect , lower part of Solvay tower is cooled , ppt of NaHCO3 are separated by vacuum filtration and washed to remove ammonium salts.
Conversion of NaHCO3 to Na2 CO3
Dry sodium bicarbonate is heated in rotary furnace called "CALCINER" to give anhydrous sodium carbonate or soda ash. Carbon dioxide is recirculated to carbonation tower.
2NaHCO3 èNa2 CO3 + CO2 + H2 O
Ammonia recovery process
When CaCO3 is heated, CaO is obtained along with CO2 . CaO is treated with water to form Ca(OH)2 .
CaO + H2 O èCa(OH)2
Quick lime is heated with NH4 Cl to form NH3 and calcium chloride (by product) . Ammonia is used again in this process.
2NH4 Cl + Ca(OH)2 èCaCl2 + 2NH3 + 2H2 O

CHEMISTRY OF s-BLOCK ELEMENTS

CHEMISTRY OF S-BLOCK ELEMENTS
EXTRACTION OF SODIUM
EXTRACTION OF SODIUM
On industrial scale sodium metal is extracted by "Down's Process".
PRINCIPLE
Down's Process is based on the electrolysis of fused NaCl.
CONSTRUCTION OF DOWN'S CELL
Down's cell consists of a rectangular container of steel. Inside of the tank is lined with firebricks. Anode is a graphite rod which projects centrally up through the base of the cell. Cathode is a ring of iron, which surrounds the anode. The anode and cathode are separated from each other by a cylindrical steel gauze diaphragm so that Na and Cl2 are kept apart. A bell like hood is submerged over the anode.
DRAW BACKS OF DOWN'S METHOD
Melting point of NaCl is 801C. At this temperature molten NaCl and Na form a metallic fog in the container which is impossible to separate.
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STEPS TO OVER COME THIS DIFFICULTY
In order to over come this difficulty instead of only NaCl, a mixture of NaCl and CaCl2 is electrolyzed in down's cell. The melting point of this mixture is 600C. At 600C no metallic fog is formed.
COMPOSITION OF CHARGE: NaCl = 42% CaCl2 = 58%
THE PROCESS
When an electric current is passed through the molten mixture of NaCl and CaCl2, NaCl decomposes in to Na+ and Cl- ion. Na+ ions migrate towards cathode while Cl- ions towards the anode. The molten sodium collects in the cathode compartment where it rises to the top and is tapped off by a pipe. Chlorine is collected at the anode.
THE CHEMISTRY OF REACTION
Fused NaCl contains sodium and chloride ions.
2NaCl è 2Na+ + 2Cl-
ELECTROCHEMICAL CHANGES
At cathode
Na+-ions migrate to cathode where they are reduced to Na.
2Na+ + 2e- è 2Na (Reduction)
At anode
Cl--ions migrate to anode and oxidised to form chlorine gas.
2Cl- è Cl2 + 2e- (Oxidation)
Overall Reaction
2Na+ + 2e- è 2Na 2Cl- è Cl2 + 2e- __________________ 2Na+ + 2Cl- è 2Na + Cl2
Reason
During electrolysis Calcium is also obtained but it does not mix with Sodium. Explain.
Answer:
During electrolysis calcium is also obtained at cathode but sodium and calcium are separated from each other due difference in density. Density of Na is 0.67gm/cc and the density of Ca is much higher than that of Na i.e. 2.54gm/cc. That's why they do not mix with each other.

Isotopes of Hydrogen

HYDROGEN
Isotopes of Hydrogen
	ISOTOPES Nuclei of the same element having same atomic number but different mass number are known as isotopes. OR Nuclei of same element having same number of proton but different number of neutron are knows as isotopes. Example 17Cl35 , 17Cl37 6C12 , 6C13 ISOTOPES OF HYDROGEN There are three isotopes of hydrogen. Protium Deuterium Tritium Protium Ordinary hydrogen is knows as protium . It has one electron ,one proton but it has no neutron. Mass number : 1 Charge number : 1 Symbol : 1H1 Percentage in natural hydrogen 99.98% Structure Deuterium Heavy hydrogen is known as deuterium. It has one electron one proton and one neutron. Mass number: 2 Charge number: 1 Symbol: 1H2 or D Percentage In Natural Hydrogen 0.0156% Ratio Protium:Deturium =1:15000 Structure Heavy water(D2O) consists of deuterium isotope of hydrogen. TRITIUM It has one electron, one proton and two neutrons. Mass number : 3 Charge number : 1 Symbol : 1H3 or 1T3 Percentage in natural hydrogen 4 X 10-15 % It is a radioactive isotope. It emits B-rays. It has a half life of 12.5 years. It is present in traces. Structure

Metallic Hydrides Polymeric Hydrides Border line Hydrides

METALLIC HYDRIDES - POLYMERIC HYDRIDES - BORDER LINE HYDRIDES
	METALLIC HYDRIDES	www.citycollegiate.com
	These are the hydrides of transition elements (except elements of group I-B and II-B).
	In transition elements there are small empty spaces among the atoms. Hydrogen gas adsorbs in these empty spaces to produce non-stoichiometric hydrides or Interstitial hydrides which are known as metallic hydrides.
	EXAMPLES
	ZrH1.92 , TaH0.76 , PrH2.3 , TiH1.7
	PROPERTIES
	1) They do not follow stoichiometric rules. 2) They behave like pure metal. 3) Bonding between metal and hydrogen is metallic bond. 4) On heating they release hydrogen in atomic state. 5) They are solids. 6) There is no true chemical reaction between metal and hydrogen in these hydrides. 7) They are not true chemical compounds. 8) They are used as reducing agent in different processes.
	POLYMERIC HYDRIDES	www.citycollegiate.com
	Hydrides of Beryllium and Magnesium are known as polymeric hydrides. In polymeric hydrides a large number of (BeH2) or (MgH2) units are joined together by hydrogen bonding to produce long chain of (BeH2) or (MgH2) .
	GENERAL REPRESENTATION
	· (BeH2)n · (MgH2)n There properties are between ionic hydrides and covalent hydrides.
	BORDER LINE HYDRIDES
	Hydrides of the elements of I-B and II-B and (In) Indium and Thallium (Tl) are known as borderline hydrides.
	EXAMPLES	www.citycollegiate.com
	CuH2 ZnH2 TlH2
	They have properties intermediate between covalent and metallic hydrides

Complex Hydrides

COMPLEX HYDRIDES
	INTRODUCTION
	Hydrides of group I-A and the group III-A are combined to form complex hydrides. Complex hydrides contains all three types of bonds.
	GENERAL FORMULA	www.citycollegiate.com
	MAH4 Where M= element of of I-A group. A= element of III-A group.
	EXAMPLES
	LiAlH4, NaAlH4, LiGaH4 etc
	PREPARATION
	LiH + AlH3 è LiAlH4 NaH + GaH3 è NaGaH4 LiH + GaH3 è LiGaH4
	IONIZATION	www.citycollegiate.com
	They ionize as M+ and AH4- LiAlH4 è Li+ + AlH4- NaAlH4 è Na+ + AlH4-
	PROPERTIES
	They are soluble in water. They are thermally stable upto 300C. They are solids. They are white in colour. They are reducing agent.
	REACTION WITH WATER	www.citycollegiate.com
	Complex hydrides when treated with water, two hydroxides are obtained with the liberation of hydrogen gas.
	NaAlH4 + 4H2O è NaOH + Al(OH)3 + 4H2

Hydrides Ionic hydrides Covalent Hydrides

HYDRIDES
	Binary compounds of hydrogen are known as hydrides.
	TYPES OF HYDRIDES
	There are six types of hydrides.
	Ionic hydrides Covalent Hydrides Polymeric Hydrides Metallic Hydrides Border line Hydrides Complex Hydrides
	IONIC HYDRIDES
	Elements of group I-A and II-A except Be and Mg form ionic hydrides. In these hydrides, bond between metal atom and hydrogen atom is ionic. Ionic hydrides are also known as Saline hydrides or Salt like hydrides because their properties are identical to salts. In ionic hydrides,hydrogen acts as H-
	GENERAL FORMULA
	For the hydrides of group I-A
	MH
	Where M represents Li, Na, K, Rb, Cs and Fs
	EXAMPLES
	LiH, NaH, KH, RbH, etc. For the hydrides of group II-A
	MH2
	Where M represents Ca, Sr and Ba
	EXAMPLES
	CaH2, SrH2 , BaH2
	METHODS OF PREPARATION
	Ionic hydrides can be prepared directly on passing hydrogen gas over hot alkali metals or alkaline earth metals.
	GENERAL EXPRESSION OF PREPARATION
	For the hydrides of group I-A 2M + H2è 2MH
	For the hydrides of group II-A M + H2 è MH2
	EXAMPLES
	For the hydrides of group I-A
	2Li +H2 è 2LiH 2K + H2 è 2KH 2Rb + H2 è 2RbH 2Na + H2 è 2NaH
	For the hydrides of group II-A
	Ca + H2 è CaH2 Sr + H2 è SrH2 Ba + H2 è BaH2
	PHYSICAL PROPERTIES OF IONIC HYDRIDES
	Ionic hydrides are solids. They are thermally very stable. They have high melting and boiling point. They are soluble in water. They are insoluble in organic compounds. They are conductors (electrolytes) of electricity.
	USES OF IONIC HYDRIDES
	To produce hydrogen gas. Reducing agent in metallurgical process. Dehydrating agent for organic solvents.
	CHEMICAL PROPERTIES OF IONIC HYDRIDES
	With Water For I-A NaH + H2O è NaOH + H2 LiH + H2O è LiOH + H2 KH + H2O è KOH + H2 For II-A CaH2 + 2H2O è Ca(OH)2 + 2H2 BaH2 + 2H2O è Ba(OH)2 + 2H2 SrH2 + 2H2O è Sr(OH)2 + 2H2
	With HCl: For I-A NaH + HCl è NaCl + H2 LiH + HCl è LiCl +H2 KH + HCl è KCl + H2 For II-A CaH2 + 2HCl è CaCl2 + 2H2 BaH2 + 2HCl è BaCl2 + 2H2 SrH2 + 2HCl è SrCl2 + 2H2
	With Ethyl Alcohol:
	C2H5OH + NaH è C2H5ONa + H2 2C2H5OH + CaH2 è (C2H5O)2Ca + 2H2
	COVALENT HYDRIDES
	Elements of group III-A to VII-A form covalent hydrides. They possess covalent bond in their structure. For example: BH3, AlH3, CH4, NH3, H2S, HCl
	Method of preparation Covalent hydrides can be prepared by two methods. Direct method N2 + 3H2 è 2NH3 H2 + S è H2S H2 + Cl2 è 2HCl Indirect method By the action of water on a suitable compound we can prepare different covalent hydrides. i) By Al4C3 Al4C3 + 6H2O è 2Al2O3 + 3CH4 ii) By Mg3N2 Mg3N2 + 6H2O è 3Mg(OH)2 + 2NH3 iii) By Ca3P2 Ca3P2 + 6H2O è 3Ca(OH)2 +2 PH3 (phosphene) iv) By PCl3 2PCl3 +6H2O è 2H3PO3 +6HCl Properties of covalent hydrides 1) Covalent hydrides are gases or liquids. e.g. Gases : CH4, NH3, H2S, Liquid : H2O, HCl 2) Liquids are volatile. 3) They have low melting and boiling points. 4) They are colorless compounds. Nature: 1) Hydrides of III-A and IV-A are neutral. 2) Hydrides of V-A are basic. 3) Hydrides of VI-A and VII-A are acidic.