Some Important Chemical Compounds

Edubull SOME IMPORTANT CHEMICAL COMPOUNDS (i) Sulphate : Those salts which are obtained by replacing hydrogen of sulphuric acid are called sulphates, e.g., Sodium sulphate Na2SO4 Potassium sulphate K2SO4 Zinc sulphate ZnSO4 Copper sulphate CuSO4 Magnesium sulphate MgSO4 Calcium sulphate CaSO4 Sodium Chloride NaCl FeSO4 Calcium Chloride CaCl2 Aluminium Chloride AlCl3 Ferrous sulphate or Iron (II) sulphate (ii) Chlorides : When hydrogen of hydrochloric acid is replaced by cation, chloride salt are formed, e.g., Stannous sulphate SnSO4 Copper chloride CuCl2 Ferric sulphate or Fe (III) sulphate Fe2(SO4)3 Nickel chloride NiCl2 Potassium chloride KCl Aluminium sulphate Al2(SO4)3 Cr2(SO4)3 Magnesium chloride MgCl2 NiSO4 Iron (III) chloride FeCl3 MnSO4 Arsenic chloride AsCl3 BaSO4 Antimony chloride SbCl3 Chromium sulphate Nickel sulphate Manganese sulphate Barium sulphate Cobalt sulphate Mercury (II) sulphate Lead sulphate CoSO4 HgSO4 PbSO4 CONTENTS  INTRODUCTION  IMPORTANT TERMS & CONCEPT  INTRODUCTION  Types of Salt : When cation replaces H+ of an acid, salt is formed. There are various types of salts. (iii) Nitrates : Those salts which are obtained by replacing hydrogen of nitric acid by action are called nitrate salts, e.g., Sodium nitrate NaNO3 Potassium nitrate KNO3 Ammonium nitrate NH4NO3 Lead nitrate Pb(NO3)2 Calcium nitrate Ca(NO3)2 Magnesium nitrate Mg(NO3)2 Aluminium nitrate Al(NO3)3 Copper nitrate Cu(NO3)2 (iv) Carbonates : When hydrogen of carbonic acid is replaced by metal ion, carbonate salts are formed, e.g., Ebull Sodium carbonate Na2CO3 Zinc carbonate ZnCO3 Iron (II) carbonate FeCO3 Potassium carbonate K2CO3 Copper carbonate CuCO3 Lead carbonate PbCO3 2. Salts. Salts are also obtained by reaction of acid with base. Cation is derived from base anion is derived from acid. The salts derived from sodium hydroxide are called sodium salts. The salt derived from potassium hydroxide are called potassium salts. Calcium hydroxide gives calcium salts, magnesium hydroxide gives magnesium slats, copper hydroxide gives copper salts and so on. 3. Diplacement Reactions. Those reactions in which more reactive metal can displace less reactive metal from its salt solution. 4. Hydrogen Carbonates. Those salts which are obtained by replacement of one hydrogen of H2CO3 are called hydrogen carbonates or bicarbonates e.g., 6. Monoprotic Acids. Those acids which give one H+ ion in aqueous solution are called monoprotic acids, e.g., HCl, HBr, HI, HNO3, HNO2 (nitrous acid), CH3COOH (acetic acid), HCOOH (formic acid). They form only one type of salts. 7. Diprotic Acids. Those acids which give two H+ ions in aqueous solution are called diprotic acids, e.g., H2SO4, H2CO3 (carbonic acid), H2SO3 (sulphuric acid), (COOH)2 (oxalic acid). They form two series of salts, one by replacing one hydrogen and another by replacing both the hydrogen atoms. Sodium hydrogen phosphate NaH2PO4 Sodium phosphate Na3PO4 Disodium hydrogen phosphate Na2HPO4 8. Triprotic Acids. Those acids which give three protons i.e. three H+ ions in aqueous solution are called triprotic acid, e.g., H3PO4 (phosphoric acid). They form three series of salts. 9. Chemical in Common Salt. The main chemical present in common salt is sodium chloride. It is obtained by neutralization reaction of sodium hydroxide with HCl (Hydrochloric acid). It is obtained on a large scale from sea water. It is found in large deposits called rock salt. Sodium hydrogen carbonate NaHCO3 Potassium hydrogen carbonate KHCO3 Calcium hydrogen carbonate Ca(HCO3)2 (i) It is used in daily food. Magnesium hydrogen carbonate Mg(HCO3)2 (ii) It is used as preservative 5. Hydrogen Sulphates. Those salts which formed by replacement of one atom of hydrogen of sulphuric acid by metal ion are called hydrogen suphates e.g. Sodium hydrogen sulphate NaHSO4 Calcium hydrogen sulphate Ca(HSO4)2 Potassium hydrogen sulphate KHSO4 Magnesium hydrogen sulphate Mg(HSO4)2 10. Uses of Common Salt. (iii) It is used for manufacture of Na metal and Cl2 (g) by electrolysis in molten state. (iv) It is used for manufacture of caustic soda. (v) It is used for manufacture of baking soda and washing soda by Solvay process. 11. Manufacture of Sodium Hydroxide. Sodium hydroxide is the most important alkali and is made commercially by electrolysis of saturated brine solution (sodium chloride). Three kinds of cells are used : Edubull Castner-Kellner Cell. In this cell, mercury flows along the bottom of the cell and is made cathode in outer compartments as shown in figure. The anode consists of number of graphite blocks. +ve carbon anodes Cl2 Spent brine out Na/Hg Out At the anode + 2Cl– –Cl2 + 2e– Strong brine in At the cathode – Na+ + e– –Na Na + Hg –NaHg Hg in Sodium amalgam Moving mercury cathode (–ve) Thee electrolysis of brine solution takes place. Since hydrogen has a over voltage (i.e.more energy is required to discharge H+ ion) at mercury cathode, sodium is preferentially discharged at cathode forming amalgam with mercury. Sodium amalgam flows out and is reacted with H2O to give NaOH. 2NaHg + 2H2O –2NaOH + 2Hg + H2 The mercury is recirculated in the cell. H2 and Cl2 are two important by-products. (i) It is deliquescent solid and absorbs moisture and CO2 finally forming solid hydrated carbonate. (ii) It can precipitate cations like Zn2+, Al3+, Pb2+, Sn2+ but these precipitates get dissolved in excess of NaOH. Zn(OH)2 + 2OH – [Zn(OH)4] – 14. Washing Soda. Its chemical formula is Na2CO3.10H2O, i.e. sodium carbonate decahydrate, i.e. one mole of Na2CO3 contains 10 moles of water of crystallization. Anhydrous sodium carbonate is called soda ash. 15. Solvay Process. It is used for manufacture of washing soda. It is also called Ammonia Soda process. Process. (i) In this process a cold and concentrated solution of sodium chloride (called brine) is saturated with ammonia. (ii) The ammonical brine is fed from the top of the carbonating tower packed with perforated plates. (iii) Carbon dioxide (CO2) is introduced from the base of the tower which reacts with NH3 and H2O to form ammonium bicarbonate (ammonium hydrogen carbonate). NH3 + H2O + CO2 – (NH4)HCO3 12. Properties of Sodium Hydroxide. 2– (viii) It is used as reagent in laboratory. Raw materials. Sodium chloride (NaCl), ammonia (NH3) and limestone (CaCO3). Fig. THE CASTNER-KELLNER CELL – (vii) It is used in absorbing poisonous gases. (Zincate ion) …..(i) (iv) Ammonia hydrogen carbonate reacts with sodium chloride (NaCl) to form sodium hydrogen carbonate and ammonia chloride. (NH4)HCO3 + NaCl –– NaHCO3 + NH4Cl Ammonium Hydrogen carbonate Sodium chloride Sodium Hydrogen Ammonium carbonate chloride …….(ii) 3– Al(OH)3 + 3OH – [Al(OH)6] (Aluminate ion) Sn(OH)2 + 4OH– – [Sn(OH)6]3– (Stannate ion) Pb(OH)2 + 2OH– – [Pb(OH)4]2– (Plumbate ion) 13. Uses of Sodium Hydroxide. (i) It is used in soap industry. (ii) It is used in paper industry (iii) It is used in textile industry (iv) It is used for preparation of pure fats and oils. (v) It is used in preparation of artificial silk (rayon). (vi) It is used in petroleum industry. (v) CO2 used in first reaction is produced by heating limestone in lime kiln (furnace). CaCO3 heat –– Limestone CaO Quicklime + CO2 Carbon dioxide (vi) Quiklime reacts with H2O to form slaked lime. CaO Calcium oxide + H2O Water –– Ca(OH)2 Calcium hydroxide (vii) Slaked lime reacts with ammonium chloride produced in reaction (ii) to generate ammonia which can be used again in reaction (i). Edubl Ca(OH)2 + 2NH4Cl –– CaCl2 + 2NH3 Calcium hydroxide Ammonium chloride Calcium chloride + 2H2O Ammonia Water Thus, most of ammonia can be recovered and reused, therefore, this process is economical. Secondly, calcium chloride is obtained as a byproduct. (vi) When treated with HCl or H2SO4, it liberates CO2 gas. Na2CO3 + 2HCl ––2NaCl + H2O + CO2 …(v) Na2CO3 + H2SO4 ––Na2SO4 + H2O + CO2 …(vi) (viii)Sodium hydrogen carbonate, formed in reaction (ii) is sparingly (partially) soluble in water and can be separated by filtration. (vii) When CO2 gas is passed through aqueous solution of sodium carbonate, sodium hydrogen carbonate gets precipitated. (ix) Sodium hydrogen carbonate is heated to form sodium carbonate. Na2CO3 + CO2 + H2O ––NaHCO3 (vii) 2NaHCO3 heat –– Na2CO3 + H2O + CO2 Sodium hydrogen carbonate Sodium carbonate Water Carbon dioxide 17. Uses of Sodium Carbonate. (i) It is used in manufacture of glass, soap, paper and other sodium compounds like borax, caustic soda, etc. CO2 formed is recirculated., i.e. used again in reaction (ii) It is used in softening of hard water. (i). (iii) It is used as washing soda in laundries. (x) Sodium carbonate is recrystallized by dissolving in water to get washing soda. (iv) It is used as cleaning agent for domestic purposes. Na2CO3 + 10H2O –– Na2CO3.10H2O Sodium carbonate (anhydrous) (vi) It is used in textile and petroleum refining. Washing soda (vii) It is used for preparation of carbonate of metals. 16. Properties of Washing Soda (i) It is a transparent crystalline solid. (ii) It contains ten crystallization. molecules of water of (iii) It is efflorescent substance (i.e. loses water of crystallization) when exposed to air. It loses nine molecules of water and forms monohydrate. Na2CO3 . 10H2O –– Na2CO3.H2O + 9H2O Sodium carbonate (decahydrate) (Sodium carbonate) monohydrate (iv) Washing soda loses all the water of crystallisation on heating and becomes anhydrous (which does not contain water of cyrstallisation). It does not decompose on heating. Na2CO3 . 10H2O Sodium carbonate (decahydrate)  –– Na2CO3. + 10H2O Soda ash (Anhydrous sodium carbonate) (v) Washing soda dissolves in water to form an alkaline solution which turns red litmus blue. It shows that its aqueous solution is alkaline in nature. Na2CO3 + 2H2O (v) It is used as laboratory reagent. 2NaOH + H2CO3 ..…(iv) (viii) It is used in fusion mixture (Na2CO3 + K2CO3) which helps in qualitative analysis i.e., in preparation of soda extract in case of insoluble salts. 18. Baking Soda (NaHCO3). Baking soda, chemically is sodium hydrogen carbonate. It is obtained as a first product in Solvay process as shown in reaction (ii). It can also be obtained by passing CO2 gas through aqueous solution of sodium carbonate as shown in reaction (vii). 19. Properties of Sodium Hydrogen Carbonate. (i) It is white crystalline solid. (ii) It is sparingly soluble in water. (iii) Its aqueous solution is alkaline in nature due to hydrolysis. The solution is weakly basic. ……..(iii) NaHCO3 + H2O NaOH + H2CO3 This solution gives yellow colour with methyl orange (indicator) but no colour with phenolphthalein. (iv) On heating, it loses carbon dioxide and water forming sodium carbonate. Edubull heat 2NaHCO3 –– Na2CO3 + CO2 + H2O (Sodium hydrogen carbonate) CaOCl2 + CO2 –– CaCO3 + Cl2 (v) When it comes in contact with H2SO4. It gives CO2 which is used in fire extinguishers. 2NaHCO3 + H2SO4 –– Na2SO4 + 2H2O + 2CO2 20. Uses of Sodium Hydrogen Carbonate . (i) It is used as antacid (medicine) under the name soda bicarbonate to neutralize excess of acidity (hyper-acidity) in the stomach. (ii) It is an ingredient of baking powder which contains NaHCO3 and tartaric acid. When baking powder is heated, sodium hydrogen carbonate decomposes to give CO2 and sodium carbonate. CO2 causes bread and cake to rise. Tartaric acid helps to remove bitter taste due to formation of Na2CO3. (iii) It is used as additive in foods. (iv) It is used in making aerated soft drinks. (v) It is used in fire extinguishers because it forms CO2 , when reacted with H2SO4.CO2 surrounds the combustible substance which helps in extinguishing fire. (vi) It is used for production of carbon dioxide. 21. Bleaching Powder (CaOCl2). Chemically, it is called calcium oxychloride. It is also called as chloride of lime. Manufacture. It is manufactured by Hasenclever's plant or in Bachmann's plant by the reaction of dry slaked lime with chlorine gas. Ca(OH)2 + Slaked lime Cl2 Chlorine (iii) It loses chlorine by the action of carbon dioxide. –– CaOCl2 Bleaching powder + H2O Water 22. Properties of Bleaching Powder (Calcium oxychloride). (i) It is a pale yellow powder. It has a strong smell of chlorine. (ii) It is soluble in water but a clear solution is never formed due to presence of impurities. 23. Uses of Bleaching Powder. (i) It is used for bleaching cotton, linen in textile industries, for bleaching washed clothes in laundry. (ii) It is used as oxidizing agent in many chemical industries. (iii) It is used for disinfecting drinking water to make water free from micro-organisms. (iv) it is used for manufacture of chloroform. (v) It makes wool unshrinkable. 24. Plaster of Paris (CaSO4. 1 H2O). 2 Chemically, Plaster of Paris is calcium sulphate hemihydrate. It is called Plaster of Paris because it is obtained from gypsum which is mainly found in Paris. Preparation. Plaster of Paris is obtained by heating gypsum (CaSO4.2H2O) at 373 K in a kiln. Heating should be done carefully. 1 3 373 K CaSO 4 .2H 2 O  CaSO4 . H 2 O  H 2 O 2 2 Gypsum Plaster of Paris 25. Properties of Plaster of Paris. (i) It is white powder. (ii) When it is mixed with water, crystals of gypsum are produced and set into hard mass. 1 3 CaSO 4 . H 2 O  H 2 O   CaSO4 .  2H 2 O 2 2 Gypsum Plaster of Paris The setting process is exothermic, i.e., heat is evolved. The setting process may be catalysed by sodium chloride while it can be retarded by borax or alum. (iii) When Plaster of Pairs is heated at 473 K, if forms anhydrous calcium sulphate which is known as Edubull dead burnt plaster of paris. It has no setting property as it takes up water very slowly. CaSO4. 1 1 473 K H2O  CaSO4 + H2O 2 2 28. Water of Crystallization. It is fixed number of water molecules present in crystalline salt, e.g, Blue vitriol CuSO4 .5H2O Glauber's salt Na2SO4.10H2O Gypsum CaSO4.2H2O Green vitriol FeSO4.7H2O (ii) It is used in making toys, decorative materials. White vitriol ZnSO4.7H2O (iii) It is used in making casts for statues, toys, surgical instruments, etc. Epsom salt MgSO4.7H2O 26. Uses of Plaster of Paris. (i) It is used for plastering fractured bones and dislocated bones so as to set them in proper place. (iv) It is used in making blackboard chalks. (v) It is used in dentistry. (vi) It is used for making smooth surface and ornate designs on walls and ceilings. (vii) It is used in laboratories for sealing air gaps in apparatus so as to make it airtight. 27. Uses of Mild Bases. (i) Washing soda is used as cleaning agent. (ii) NaHCO3 acts a antacid. (iii) Sodium carbonate is used in removing permanent as well as temporary hardness of water.