CHEMISTRY GRADE: - XI (ISC)

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1 CHEMISTRY GRADE: - XI (ISC) COMPOUNDS OF GROUP 1 Sodium chloride Uses 1. Sodium chloride is an useful constituent of our food. 2. It is used in the manufacture of sodium, sodium hydroxide, washing soda, hydrogen chloride, chlorine. 3. It is used in freezing mixture. 4. It is used for the purification of soap. 5. It is used for the regenerating ion exchange resin. Sodium Hydroxide Castner - Kellner cell Principle It consist of a large rectangular tank divided into two compartments with the help of a slate portion not touching the bottom. A layer of mercury is provided at the bottom of the cell. The

2 mercury is made to flow form one compartment to the other by giving rocking motion to the tank with the help of eccentric wheel. The left hand compartment is filled with graphite anode whereas the right hand compartment is filled with iron cathode. The left hand compartment contains brine solution and the right hand compartment contains a very dilute solution of sodim hydroxide.mercury at the bottom of the tank acts as an intermediate electrode i.e acts as a cathode in the left hand compartment and as a anode in the right hand compartment. On passing electric current the following reactions take place. Left Hand compartment Na + e Na Na + Hg --- Na/ Hg [sodium amalgam] Sodium ion gets discharged at the mercury cathode and sodium formed dissolves in mercury to form sodium amalgam. Cl - e - -- Cl 2Cl Cl 2 Chlorine is liberated at the graphite anode which is led out through an exit at the top. Sodium amalgam passes into the right hand compartment due to rocking motion. Right Hand compartment Here the sodium amalgam acts as the anode and iron rods act as cathode. Anode : Na - amalgam Na + + Hg + e Cathode : 2H2O + 2 e H2 + 2OH Na + + OH > NaOH Thus concentration of NaOH solution goes on increasing. The concentrated of sodium hydroxide solution ( about 20% ) is taken out from inner compartment and evaporated to dryness and cast into sticks. Sodium Carbonate (Soda Ash) Principle: When carbon dioxide is bubbled through brine solution ( 28% NaCl) saturated with ammonia,nahco3 is formed. NH3 + HCl +CO NH4CO3 NH4CO3 + NaCl NaHCO3 + NH4Cl NaHCO3 formed is insoluble.it is filtered and then ignited to get sodium carbonate.

2NaHCO3 -------- Na2CO3 + H2O Equations of Solvay process 1. Saturation of brine with Ammonia - About 30% of brine solution is pumped into ammonia absorber.

3 2NaHCO Na2CO3 + H2O Equations of Solvay process 1. Saturation of brine with Ammonia - About 30% of brine solution is pumped into ammonia absorber. A mixture of ammonia and a small amount of carbon dioxide is bubbled through the brine solution so that it gets saturated with ammonia. 2NH3 + H2O + CO (NH4)2CO3 2. Carbonation - The ammoniated brine is introduced from the top of the carbonating tower.carbon dioxide is introduced from the bottom of the tower (NH4)2CO3 + H2O + CO NH4HCO3 NH4HCO3 + NaCl NH4Cl + NaHCO3 3. Calcination of sodium bicarbonate 2NaHCO Na2CO3 + CO2 + H2O Solvays process cannot be used for the manufacture of K2CO3 because KHCO3 formed as an intermediate is highly soluble in water and cannot be separated by by filteration.. Uses 1. It is used in the manufacture of glass, borax, soap, caustic soda 2. It is used for washing purpose in laundry. 3. It is used for softening hard water. 4. A mixture of sodium carbonate and potassium carbonate is used as a fusion mixture. 5. It is used in paper, textile, and paint industries. 6. It is used as a reagent in the laboratory.

4 Sodium bicarbonate (Baking soda) Preparation from sodium carbonate Na2CO3 + H2O + CO NaHCO3 Uses 1. It is used as component of baking powder. 2. It is used in medicine as a mild antiseptic for skin infection 3. It is used in fire extinguisher. 4. It is used in making effervescent drinks. 5. It is also used as a reagent in the laboratory. Sodium Thiosulphate (Hypo) crystals [ Na2S2O3. 5H20] Preparation: By boiling sulphur with aq solution of sodium sulphate[ 373 K] Na2SO3 + 1/8 S Na2S2O3 Reactions 1. With iodine 2Na2S2O3 + I NaI + Na2S4O6 [sodium tetrathionate] This reaction is the basis of iodometric titration in volumetric analysis. Iodine oxidises Na2S2O3 - Na2S4O6 and the colour of iodine is discharged. 2. With dilute acid Na2S2O3 + HCl NaCl + SO2 + H2O +S Na2S2O3 + H2SO Na2SO4 +SO2 + H20 +S 3. With AgNO3 [white ppt changes to yellow to brown to black due to formation of silver sulphide] Na2S2O3 + 2AgNO Ag2S2O3 + 2NaNO3 Ag2 S2O3 + H2O Ag2S + H2SO4 Uses 1. As a fixer in photography. 2. As antichlor in bleaching industry to remove the excess of chlorine from textile fibres. 3. As a reagent in the laboratory for iodometric titrations. 4. In extraction of silver and gold. Biological importance of Sodium 1. Sodium ions regulate the flow of water across cell membranes and in the transport of sugars and amino acids into cells. 2. They take part in the transmission of nerve signals.

5 Biological impotance of Potassium 1. In cell fluids they activate many enzymes and participate in oxidation of glucose to produce ATP which act as a source of energy for energy requiring reactions. K + and Na + ions participate in transmission of nerve signals and are called sodium potassium pump which operates across the cell membranes. Compounds of Group 2 (Alkaline Earth Metals) 1. Magnesium Chloride hexahydrate ( MgCl2.6H2O) :- Preparation:- MgO + 2HCl MgCl2 + H2O Effect of Heat :- On heating it undergoes partial hydrolysis to form a basic chloride which On further heating decomposes to form magnesium oxide. MgCl2.6H2O Δ Mg(OH) Cl + HCl + 5H2O Mg(OH)Cl Δ MgO + HCl. Uses:- i) Magnesium chloride is used in making Sorel s Cement which is used as a dental filling, as a substitute for tiles and for cementing glass with metals. ii) It is used in lubricating cotton thread in spinning. iii) It is used in the preparation of magnesium oxide and other magnesium compounds. 2. Calcium Oxide: - It is prepared by heating limestone in a rotatory Kiln at K. Preparation: - CaCO3 CaO + CO2 ΔH = 179.9KJ Chemical Properties:- i) With water: - CaO + H2O Ca(OH)2. ΔH = -15 Kcal. This process is known as slaking of lime and the product is called as slaked lime. This process is exothermic in nature. ii) With Carbon dioxide :- CaO + CO2 CaCO3 iii) With Silica:- CaO + SiO2 CaSiO3 ( calcium silicate)

6 Uses:- i) It is used in purification of sugar. ii) It is used for drying gases and alcohol iii) It is used as a building material and for white washing. iv) In agriculture, it is used as a disinfectant and germicide. 3) Calcium Carbonate:- Preparation: - Ca(OH)2 + CO2 CaCO3 + H2O Uses:- i) Limestone is used for the manufacture of lime, cement, glass and washing soda. It is also used in the extraction of several metals. ii) Marble is used as a building material for construction purposes. iii) Precipitated chalk is used in the manufacture of paints, distempers, cosmetic powder, medicines, toothpaste etc.. 4) Plaster of Paris:- It is a hemihydrate of calcium sulphate with the formula CaSO4.1/2 H2O. Preparation:- It is prepared by partial dehydration of gypsum by heating it in a kiln to K with agitation. Uses:- 2CaSO4.2H2O (CaSO4)2.H2O + 3H2O i) It is used for making moulds for casting. It expands on setting and so it s very useful for this purpose. ii) It is used for making statues, models and other decorative items. iii) It is used for making various patent plasters used in surgery for plastering fractured parts of the body. iv) It is used in building industry. v) It is also used in making blackboard chalks. 5) Cement: - It is a finely grounded mixture of various silicates of calcium and aluminium. It is also known as Portland cement. It settles and becomes hard on mixing with water. Manufacture:- The main raw materials needed for the manufacture of cement are limestone and clay (Silica, alumina, iron-oxide) These raw materials are mixed either by dry process or by wet process.

7 Dry Process: - It is used when the raw materials are hard and dry. The limestone is broken into small pieces and mixed with clay in a proper proportion. The mixture is powdered and pulverized to get a uniform mixture known as raw meal. Wet Process: This process is used when the raw materials are soft and damp. Clay is washed with water and tehn mixed witrh crushed limestone in proper proportion. This mixture is then finely grounded and homogenized. The product is known as slurry. Burning in rotary Kiln:- the raw meal or slurry is charged from one end of the rotary kiln. The rotary kiln is consist of a steel cylinder resting on rollers and made to revolve slowly. The kiln is heated by a blast of burning coal blown from the other side. Due to revolving of kiln, the charge moves from one end to the other and gets heated to K. Folowing reactions takes place in the kiln: CaCO3 CaO + CO2 2CaO + SiO2 2CaO.SiO2 3CaO + SiO2 2CaO.SiO3 3CaO + Al2O3 3CaO.Al2O3 4CaO + Al2O3 + Fe2O3 4CaO.Al2O3.Fe2O3 The resulting product is known as cement clinker. It is then taken to a revolving tube known as cooler where it gets cooled. Grinding with gypsum:- Cement clinker is mixed with 2-3% gypsum and ground to a fine powder. Gypsum is added to regulate the setting time of cement. The fine powder thus obtained is Portland Cement. Biological importance of Magnesium, and Calcium:- Magnesium 1. It an important constituents of Chlorophyll the green colouring matter present in plants. 2. MAgensium ion si also present in cellular fluid in animal bodies. Calcium 1.Calcium ion is present as phosphates in the bones of both human and animals. They are essential for the formation of bones and teeth. 2.It plays a very important role in muscle contraction.

8 3. Magnesium ion is essential for activating phosphate transfer enzymes. 4. Magnesium and calcium ions transmit electrical impulses along with the nerve fibre and help in contraction of muscles. 3.Calcium ion are essential for maintain rhythm of heart and for clotting of blood. 4.The hydrolysis of pyrophosphate to release energy is controlled by calcium ions. x x x x x x

Sodium Peroxides (Na 2 O 2 ): Preparation: It is formed by heating the metal in excess of air or oxygen at 300, which is free from

Sodium Peroxides (Na 2 O 2 ): Preparation: It is formed by heating the metal in excess of air or oxygen at 300, which is free from S-Block Elements Generally one question was asked every year from this topic. This is completely theoretical and little memory based. Last minute revision generally helps. The general trends in the properties