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In alcohols, the oxygen of the -OH group is attached to sp 3 hybridised carbon by a sigma bond formed by the overlap of sp 3 hybrid orbital of carbon with an sp 3 hybrid orbital of oxygen. The figure shown below illustrates the bonding in methanol. The C-O-H bond angle in alcohol is slightly less than the tetrahedral angle (109 0 28). It is due to the repulsion between the unshared electron pairs of oxygen. In phenols, the –OH group is attached to sp 2 hybrid carbon of an aromatic ring. The C-O-H bond angle in phenol is 109 0 . The carbon-oxygen bond length (136pm) in phenol is slightly less than that in methanol (142pm). This is due to partial double bond character on account of the conjugation of unshared electron pair of oxygen with the aromatic ring. In ethers, the four electron pairs, ie; the two bond pairs and two lone pairs of electrons around oxygen are arranged approximately in a tetrahedral arrangement. The c-o-c bond angle (111.7 0 in methoxy methane) is slightly greate...

The pH of acidic and basic buffer can be calculated by Henderson – Hasselbalch equations. Consider an acidic buffer HA + A - HA H + + A - K a = [H + ] [A - ] / [HA] [H + ] = K a [HA]/[A - ] [H + ] = K a [acid]/[salt] There fore pH = -log[H + ] pH = pK a + log [salt]/[acid] when, [salt]/[acid] = 1 , pH = pK a Since pK a of an acid is a constant at constant temperature, the pH of the buffer is constant. Thus buffer capacity is maximum in a solution containing equivalent amount of acid and its salt. The pH of basic buffer is also given by Henderson – Hasselbalch equation BOH B + + OH - K b = [B + ][OH - ]/[BOH] [OH - ] = K b [BOH]/[B + ] pOH = pK b + log [salt]/[base] pH = 14 – pOH = 14 – [pK b + log [salt]/[base]]

The property of a buffer solution to resist change in its pH value even when small amounts of the acid or the base are added to it is called buffer action . Consider the acidic buffer solution containing acetic acid and sodium acetate. They dissociate as CH3COONa <=======> CH3COO - + H + CH3COONa <=======> CH3COO - + Na + When a few drops of an acid, HCl is added to this buffer solution, the H + ions combine with CH3COO - ions to form weakly ionized molecules of CH3COOH. CH3COO - + H + <=======> CH3COOH Thus H + ion concentration does not change and hence the pH of the solution remains constant. When a few drops of base, NaOH is added to the buffer solution, hydroxyl ions of the base neutralize the acid, forming salt and water. Similarly, in a basic buffer solution of NH4OH and NH4Cl, they dissociates as NH4OH <======> NH4 + + OH - NH4Cl ----------> NH4 + + Cl - When a few drops of a base added, the OH - ions given by it combine with NH4 + ions to ...

Maintenance of PH in blood and in intracellular fluids is absolutely crucial to the processes that occur in living organisms. This is primarily because the functioning of enzymes is sharply pH dependent. The normal pH value of blood plasma is 7.4 and several illness or death can result from sustained variations of a few tenths of pH unit. Also many medical and cosmetic formulations require that these must be kept and administered at a particular pH. There are solutions which resist the change in pH on addition of small amount of acid or alkali and are called Buffer solution . For example a mixture of H 2 CO 3 and HCO 3 - is a natural buffer system which maintains the pH of blood. A buffer that is widely used in clinical laboratory and in biochemical studies in the physiological pH range is prepared from tris amino methane (hydroxy methyl) (THAM) [(HOCH 2 )3CNH 2 ]. In order for a solution to act as a buffer it must have two components, one of which is able to neutralize acid and the o...

Qualitative analysis of cations is largely based on the principle of solubility product and common ion effect. Cations are separated in to six groups depending on the solubility of their salts. Group-1 as insoluble chlorides Only Ag + , Hg 2+ and Pb 2+ form insoluble chlorides since they have low values of K sp . Group-2 as insoluble sulphide in acidic medium H 2 S <========> H + + HS - ; K 1 - first ionization constant HS - <========> H + + S 2 - ; K 2 – second ionization constant [S 2 - ] = K 1 K 2 [H 2 S]/[H + ] 2 K sp values of second group sulphides (PbS, CuS, SnS, HgS, As 2 S 3 , Bi 2 S 3 , Sb 2 S 3 ) are very low. In acidic buffer, [S 2 - ] is decreased due to common ion effect and this results in the precipitation of Pb 2+ , Cu 2+ etc of second group as their sulphides. Third and fourth group sulphides have high value of K sp , hence they remain soluble. Group- 3 as insoluble hydroxide in basic buffer of NH 4 OH and NH 4 Cl The concentration of OH - in a...

The solubilityof ionic solids in water varies depending on a number of factors like lattice enthalpy of the salt and tha solvation enthalpy of the ions in a solution. As a general rule, for a salt to be able to dissolve in a particular solvent, its solvation enthalpy must be greater than its lattice enthalpy. Each salt has its characteristic solubility, which depends on temperature. We can classify salts on the basis of their solubility in three categories. Soluble - Solubility > 0.1 M Slightly soluble - 0.01 M < solubility < 0.1M Sparingly soluble – solubility < 0.01M We have now consider the equilibrium between the sparingly soluble ionic salt and its saturated aqueous solution. A solution which remains in contact with excess of the solute is said to be saturated . The amount of a solvent () in 100 ml or 1L) to form a saturated solution at a given temperature is termed as the solubility of the solute in the solvent at that temperature. For a sparingly soluble salts like ...

The decrease in the ionization of a weak electrolyte by the presence of a common-ion from a strong electrolyte, is called the common ion effect . Ionisation of CH 3 COOH (weak acid) is decreased by the addition of CH 3 COONa (CH 3 COO- being the common ion) CH 3 COOH CH 3 COO - + H + ……………………….. (A) CH 3 COONa -----------> CH 3 COO - + Na + In the presence of CH 3 COO - equilibrium (A) shifts in backward direction. Ionisation of H 2 S (weak acid) is decreased by the addition of HCl (H + being the common ion) H 2 S 2H + + s 2- HCl H + + Cl - Ionisation of NH 4 OH (weak base) is decreased by the addition of NH 4 Cl (NH4 + being the common ion) NH 4 OH NH 4 + + OH - NH 4 Cl --------------> NH 4 + + Cl - Solubility of a sparingly soluble salt is decreased by the addition of common ion. Presence of AgNO 3 or KCl decreases the solubility of AgCl. AgCl Ag + + Cl - AgNO 3 Ag + (common ion) + NO 3 - KCl K + + Cl - (common ion) The common ion effect is thus ba...

Determination of λ0M (limiting molar conductivity) for weak electrolytes It is not possible to determine the λ 0 M for a weak electrolyte by the extrapolation of λ M versus √c plot. But it can be calculated from Kohlrausch’s law. Consider the weak electrolyte CH3COOH. According to Kohlraush’s law, λ 0 CH3COOH = λ 0 H+ + λ 0 CH3COO- ………………………………… (Equation 1) We can experimentally determine the λ 0 M of strong electrolytes such as HCl,CH3COONa and NaCl. From Kohlraush’s law, λ 0 HCl = λ 0 H+ + λ 0 Cl- ……………………………………. (Equation 2) λ 0 CH3COONa = λ 0 Na+ + λ 0 CH3COO- ………………………………… (Equation 3) λ 0 NaCl = λ 0 Na+ + λ 0 Cl- ……………………………………. (Equation 4) Substracting equation 4 from the sum of equations 2 and 3, we get, λ 0 HCl + λ 0 CH3COONa - λ 0 NaCl = λ 0 H+ + λ 0 Cl- + λ 0 CH3COO- + λ 0 Na+ - λ 0 Na+ - λ 0 Cl- = λ 0 H+ + λ 0 CH3COO- = λ 0 CH3COOH Thus by measuring the molar conductance values of NaCl, HCl and CH3COONa, one can easily determi...

Kohlrausch's law of indendent migration of ions states that the molar conductance of infinite dilution (limiting molar conductivity ) is the sum of the individual contributions of the anions and cations of the electrolyte. It can be given in the mathematical form as: λ 0 M = v + λ 0 + + v - λ 0 - λ 0 + and λ 0 - are the limiting molar conductivity of cation and anion respectively. For NaCl, λ 0 M = λ 0 Na+ + λ 0 Cl- And for Al2(SO4)3, λ 0 Al2(SO4)3 =2 λ 0 Al3+ + λ 0 SO4 2-

In the laboratory phosphine is prepared by heating white phosphorus with concentrated caustic alkali solution in an inert atmosphere of oil gas or CO2. P4 + 3NaOH + 3H2O ------------> 3NaH2PO2 (Sodium hypophosphite) + PH3 (phosphine) Metal phosphides on hydrolysis form phosphine Ca3P2 + 6H2O ------------> 3Ca(OH)2 + 2PH3 A pure sample of phosphine can also be prepared by heating phosphorous acid 4H3PO3 ---------------> 3H3PO4 + PH3 Phosphine has pyramidal structure and is a weaker base than NH3

The main oxides of phosphorus are phosphorus trioxide (P4O6) and phosphorus pentoxide (P4O10) . Phosphorous trioxide is regarded as the anhydride of phosphorous acid (H3PO4). phosphorus trioxide (P4O6) is prepared by heating phosphorous in limited supply of oxygen. P4O10 is prepared by burning white phosphorous in excess of air or oxygen. P4 + 3O2 -------------> P4O6 P4 + 5 O2 ------------> P4O10 P4O10 has great affinity for water and hence it is used as a dehydrating agent. It can dehydrate HNO3 and H2SO4 to yield N2O5 and SO3 respectively. 2H2SO4 + P4O10 ------------> 2SO3 + 4HPO3 P4O6 and P4O10 dissolves in water to give phosphorus acid and orthophosphoric acid respectively. P4O6 + 6H2O -------------> 4H3PO3 P4O10 + 6H2O --------------> 4H3PO4 Related article oxyacids of phosphorus

Sulphur occurs in nature in the elemental forms, as metal sulphides and as sulphates. Sulphur also occurs as H2S present in natural gas. Sulphur is extracted by the following methods 1. Frasch process In this process, sulphur is extracted from underground deposits by pumping super heated steam down the beds to melt the sulphur and then blown out the molten sulphur with compressed air. 2. Extraction of sulphur from natural gas Natural gas contains a large amount of hydrogen sulphides (H2S). Hydrogen sulphide is first absorbed in monomethanolamine and then converts H2S into sulphur by the following reactions. 2H2S + 3O2 ------------> 2SO2 + 2H2O 2H2S + SO2 ------------> 3/8 S8 + 2H2O (at 673K and Fe2O3 as catalyst) Related article extraction of aluminium extraction of copper

Xenon trioxide (XeO3) XeO3 prepared by the slow hydrolysis of XeF6 XeF6 + 3H2O ------------> XeO3 + 6HF Xenon trioxide is soluble in water and its aqueous solution is weakly acidic. XeO3 + H2O <--------> H+ + HXeO4 – Xenate ion XeO3 has pyramidal structrure in which Xe is in sp3 hybridisation. Xenon tetroxide (XeO4) It is prepared by treating barium perxenate (Ba2XeO6) with anhydrous sulphuric acid. Ba2XeO6 + 2H2SO4 -----------> XeO4 + 2BaSO4 + 2H2O Xenon tetroxide is highly unstable and has tetrahedral structure. Related article fluorides of xenon For more detail visit indiastudychannel.com

Hydrogen sulphide is prepared in laboratory by the action of dilute HCl or dilute H2SO4 on ferrous sulphide in Kipp’s apparatus. FeS + H2SO4 ---------->4 + H2S Physical properties It is colourless gas with the smell of rotten eggs. It is denser than air and is soluble in water. Chemical properties 1. Combustibility Hydrogen sulphide burns in limited supply of oxygen to form sulphur. In presence of excess of oxygen, it gives sulphur dioxide. 2. Acidic property H2S is a weak dibasic acid and forms two types of salts namely bisulphides and sulphides NaOH + H2S ----------> NaHS + H2O 2NaOH + H2S ----------> Na2S + 2H2O 3. Action with metals When H2S is passed over hot metals the sulphides and hydrogen are formed Cu + H2S -----------> CuS + H2 4. Hydrogen sulphide in qualitative analysis H2S precipitates metal sulphides having characteristic colours from metal salt solutions in acidic or alkaline medium. Therefore H2S is used in qualitative analysis to identify metal ions belong...

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It is prepared by boiling sulphur with an aqueous solution of sodium sulphate Na2SO3 + 1/8 S8 ------> Na2S2O3 Properties Sodium thiosulphate is a water soluble crystalline substance. a) Reaction with iodine Sodium thiosulphate is oxidised by iodine to form sodium tetra thionate. This reaction is the basis of iodometric titrations. 2Na2S2O3 + I2 ---------> Na2S4O6 + 2NaI b) Reaction with chlorine Sodium thiosulphate can remove excess chlorine by forming HCl. Hence it is used as an antichlor. Na2S2O3 + Cl2 + H2O -----------> Na2SO4 + 2HCl + S c) Reaction with silver halides Silver halides dissolve in sodium thiosulphate solution due to formation of a complex sodium argento thiosulphate. This reaction is the basis of its use in photography as fixer. AgCl + Na2S2O3 -------------> NaAgS2O3 + NaCl

The stable oxides of sulphur are sulphur dioxide (SO2) and sulphur trioxide (SO3) Sulphur when burnt in air form sulphur dioxide. S8 + 8O2 -------------> 8SO2 SO2 is a gas at room temperature. It exists as descrete SO2 molecule with angular structure. SO3 is an acidic oxide and exist as planar triangular molecule in gas phase. In solid state, SO3 exist either as cyclic trimer or linear chain polymer.

Bleaching powder is a mixture of calcium hypochlorite, Ca(OCl) 2 and calcium chloride CaCl 2 . Thus, its chemical composition is Ca(OCl) 2 + CaCl 2 or can be written as CaOCl 2 or Ca(OCl)Cl (Calcium chloro hypochlorite). Bleaching powder is manufactured by passing chlorine gas over dry slaked lime at 40 0 C. Ca(OH) 2 + Cl 2   ←  CaOCl 2 + H 2 O Properties It is an yellowish white powder with strong smell of chlorine and is soluble in water. Aqueous solution of bleaching powder contains chloride and hypochlorite ions. CaOCl 2    ↔  Ca 2+ + Cl - + ClO - In presence of small quantities of dilute acids, it liberates nascent oxygen. Thus it act as oxidizing agent. 2CaOCl 2 + H2SO 4    →  CaCl 2 + CaSO 4 + 2HClO HClO  ←  HCl + [O] When bleaching powder is treated with excess of dilute acid or CO2, whole of the chlorine present in the molecules is evolved. The amount chlorine so liberated is called available chlorine. A ...

Nitrogen is the first element of group 15 of the periodic table and has the electronic configuration 1s2 2s2 2p3. Like oxygen and hydrogen, nitrogen exists in its elemental forms as a diatomic molecule. Nitrogen forms a variety of compounds in all oxidation states ranging from -3 to +5. The common oxidation states are -3, +3 and +5. Molecular nitrogen comprises 78% by volume of the atmosphere. Dinitrogen is a colourless, odourless, tasteless gas. It has two stable isotopes, 14N and 15N. It is non toxic. Dinitrogen is chemically unreactive a at ordinary temperature. At higher temperatures dinitrogen directly combines with some metals and nonmetals to form ionic and covalent nitrides. Some examples are 6Li + N2 --------> 2Li3N 3Mg + N2 --------> Mg3N2 In laboratory, dinitrogen is prepared by treating an aqueous solution of ammonium chloride with sodium nitrite. NH4Cl + NaNO2 -------> N2 + 2H2O + NaCl Uses of dinitrogen Dinitrogen is mainly used in the manufacture of ammonia and ...

Uranium is the last element occurring in nature. The elements coming after uranium are called transuranium elements. They are all synthetic in nature and are man made. They are radioactive and most of them have short half lives. For example :- 238 U 92 + 1 n 0 → 239 U 92 → 239 Np 93 + 0 e -1 Uranium → Neptunium 239 Np 93 → 239 Pu 94 + 0 e -1 Neptunium → Plutonium ( Here the Uranium(238,92) is abundant and non fissionable, It can be made into fissionable by reaction given above ) The element beyond actinides in the periodic table form atomic number 104 to 112 are called transactinide elements. These elements are rutherfordium (Rf), dubnium (Db), Seaborgium (Sg) etc. The nuclear reactions for the preparation of some of the transactinide elements are given below. 249 Cf 98 + 12 C 6 → 257 Rf 104 + 4 1 n 0 Californium → Rutherfordium 249 Cf 98 + 15 N 7 → 257 Db 104 + 4 1 n 0 Californium → Dubinium For more detail visit Indiastudychannel .com

Many chemical substances such as flavourings, sweeteners, dyes, antioxidants, fortifiers, emulsifiers and antifoaming agents are added to food for their preservation and enhancing their appeal. With the exception of preservatives, fortifying agents, antioxidants and artificial sweeteners. The other classes of chemicals are added either for ease in processing or for cosmetic purposes. In real sense, these substance have no nutritive value. Preservatives Usually food is most appetizing when it comes from the production line in the food processing plant. But, during storage and distribution undesirable changes occur in flavour, colour, texture and appetitic appeal. To delay these changes many chemical substances are added to food. These chemicals are called food preservatives. They prevent spoilage of food due to microbial growth. commonly used preservative is sodium benzoate (C6H5COONa).In order to preserve colourless food materials potassium metabisulphite or sodium metabisulphite is us...

The metals prepared by different methods contain impurities. The methods used for the purification of metals are called refining. The refining method depends on the nature of metal and the nature of impurities. Some common methods are as follows 1. Distillation Volatile metals like zinc and mercury are purified by boiling the impure metal to get vapors of the pure metal which is condensed and collected. 2. Liquation Low melting metals like tin and lead are purified by this method. The impure metal is melted on the sloping floor of a furnace. The metal melts and flows down leaving behind the high melting impurities. 3. Poling Impure metal is melted and stirred with green logs of wood. The impurities rise to the surfaces, get oxidised and removed as gases (CO2) or slag. The metal may get oxidised (eg:- Cu to Cu2O). The hydrocarbons in green wood reduces the metal oxide to the metal. Example:- Refining of impure Cu and Sn. 4. Cupellation Impure silver and gold contain base metals like lea...

Mercury forms halides in the two oxidation states, +1 and +2. 1. Mercury(1)Chloride(Hg2Cl2) Mercury(1) chloride or mercurous chloride is known as calomel. Preparation Mercury(1)chloride is prepared by heating a mixture of mecury(2)chloride and mercury in iron vessel. HgCl2 + Hg -------> Hg2Cl2 It can also be obtained by reduction of mercury(2)chloride by reducing agents like tin(2)chloride in limited quantity. 2HgCl2 + SnCl2 --------> HgCl2 + SnCl4 Properties When heated, mercury(1)chloride decomposes into mercury(2)chloride and mercury. Hg2Cl2 -------> HgCl2 + Hg The action of aqueous ammonia on the solid mercury(1)chloride gives a mixture of black finely divided mercury and white mercury amino chloride. This reaction is an example of disproportion reaction. Hg2Cl2 + 2Nh3 -------> Hg(NH2)Cl + Hg + NH4Cl Uses of mercury(1)chloride Calomel is used in making standard calomel electrodes used as secondary reference electrode. It is also used as a purgative in medicines. 2. Merc...

Preparation Silver nitrate is prepared by dissolving silver in dilute nitric acid. 3Ag + 4HNO3 ------> 3AgNO3 + 2H2O + NO Properties Silver nitrate on heating decomposes to form silver, nitrogen dioxide and oxygen. 2AgNO3 ---------> 2AgNO2 + O2 AgNO2 ---------> Ag + NO2 Silver nitrate is also decomposed by organic matter, such as glucose, paper, skin and cork. It has also a caustic and destructive effect on organic tissues. Uses of silver nitrate Large quantities of silver nitrate are used in the production of light sensitive plates, film and papers. In the laboratory it is used as a reagent for the detection of halide ions. It is used in making inks and hair dyes. In small doses, silver nitrate is used as a medicine for nervous diseases. Silver halides Silver fluorides may be prepared by the action of hydrofluoric acid on silver(1) oxide. Ag2O + 2HF -------> 2AgF + H2O Silver chloride, silver bromide and silver iodide are prepared by the action of silver nitrate on sodium ...

Copper sulphate penta hydrate is known as blue vitirol and is the most common oxosalt of copper(2) Preparation Copper sulphate is prepared industrially by blowing a current of air through copper scrap and dilute sulphuric acid. 2Cu + 2H2O + O2 --------> 2CuSO4 + 2H2O The crude copper(2) sulphate solution obtained contain iron(2) sulphates as impurity Dilute nitric acid is added to oxidize iron(2) to iron(3) sulphate which remains in solution after crystallization and CuSO4 5H2O crystallizes out. The crystalline copper(2) sulphate, CuSO4 5H2O has the structure in which four water molecules are coordinated to the central copper cation in square planar structure. The fifth water molecule is held by hydrogen bonds between a sulphate anion and a coordinated water molecule. The fifth hydrogen bonded water molecule is deeply embedded in the crystal lattice and hence not easily removed. Properties 1. Copper sulphate penta hydrate is a blue coloured crystalline solid, soluble in water. 2. Ac...

The reaction between an acid and a base is called neutralization. It is very fast and the equilibrium constant for a neutralization reaction is so large that it nearly proceeds to completion. An acid-base titration is a simple and convenient volumetric method for quantitatively estimating the concentration of one, if that of the other is known. A known volume of the solution of an acid or base is transferred to a titration flask with the help of a pipette. we add indicator and start adding known volumes of the other solution in steps with the help of a burette. The point at which the reaction is observed to be complete is called the end point of the titration and is noted by the change in the colour of the indicator. For accurate estimation it is necessary for it to coincide with the equivalence point corresponding to the stoichiometric amounts of the acid and base in the neutralization reaction. A number of weak organic acids and bases which can change its colour with in...

The important fluorides of xenon are xenon difluoride(XeF2), Xenon tetrafluoride(Xef4) and xenon hexafluoride. 1. Xenon difluoride(XeF2) It is prepared by heating a mixture of Xenon and fluorine in the ration 2:1 at 400 degree Celsius and 1 bar pressure in a sealed nickel tube. Xe + F2 ---Ni----> XeF2 XeF2 undergoes hydrolysis when treated with water an d evolves oxygen. 2XeF2 + 2H2O -------> 2Xe + 4HF + O2 In XeF2, Xenon is sp3d hybridised and the molecule has linear structure as shown. 2. Xenon tetrafluoride (Xef4) It is prepared by heating a mixture of Xe and F2 in the molecular ratio 1:5 at 400 degree Celsius and 6 atm in a sealed nickel tube. Xe + 2 F2 ---------> XeF4 XeF4 react with water and produces explosive XeO3 6 XeF4 + 12 H2O ---------> 2 XeO3 + 4 Xe + 3O2 + 24 HF In XeF4, Xenon is in sp3d2 hybridised state and has square planar geometry. 3. Xenon hexafluoride (XeF6) It is prepared by heating a mixture of xenon and fluorine in the ration 1:20 at 300 degree...