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CS, interesting solution< 433, (0 als like S, P, I, Se are are dis, , discs., Soluble jn ite 'Scussed below ;, , xo ons of alkali metals in liquiq ammenis Wt, i iki . ey cern Nia, oa ost rae of liquia ammonia is its f, he" olutions anc! extremely S its ability to dissolve alkali metals. The, , ;, (iB tal solutions are ; 800d electric,, , ‘ al conductors, The important characteristics, ‘These are blue in colour and the Colour jg j, , when the concentration of the metal ng independe, tallic pepertance. S incre,, 5 These solutions are conducting, , (i These solutions: are, (i concentration., ents ar ', @ a everal diay and dry, Sodium solutions in liquid ammonia are stable and can, , cA, i) nt of the metal dissolved., My ‘ased, the colour changes to bronze and, and sh, , OW strong re, paramagnetic 8, , ducing, properties., and the para ‘, , Magnetic character decreases with, , i metals are di in liquj ;, | when alkali Bey ssolved in liquid ammonia, they ionize to give metal ions and valence, yao #8, Na eines Nat +, goth the alkali metal ion and electron become solvated by ammonia molecules., Nat +N eee {Na(NH,),]*, Ammoniated, cation, e +yNH, —+> le(NH3),F, Ammoniated, electron, , The complete reaction may be written as :, , Na *¢N_, [Na*(NH,),]* + [e(NH,), loniated electrons are responsible for blue colour of the solution. The electrical, is also due to the ammoniated cations and ammoniated electrons. As the concentration, on is increased, the ammoniated cations and electrons associate resulting in a decrease, i Re solutions of alkali metals in liquid ammonia are metastable and when catalysed, 0 decomposition. :, , , , , , , , , 1, [e(NH,),- > NH, + 5H, + y fr 1)NH,, , As ; j , the blue colour changes to bronze and finally the blue, is BR ciiocher epee the alkali metal ammonia solutions, alkali metal can, , , , , , , , , tongly reducing character of these solutions is due to the presence of readily available, , Portant application of alkali metal solutions in organic chemistry is the reduction of, , jounds., aha a ion thoroughly studied non-aqueous solvent. Some of, By, ed, the li, , i wt, Sand disadvantages as a solvent are given belo, , ee ia as a Solvent ee dl, ae wrciais 2 ithout chemical reaction is one of the greatest advantages, Solution of alkali m, , : i Is can be recovered fr, id ammonia as a solvent. The dissolved alkali metals can | ‘ om the, "Vaporation. ay

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-_, , , , , , , , , , , , , , , , , , , agents, even 5, ammono acids, , arsine etc., , n water., , , , , , rong reducing,, , id ammonia act as, pare silane,, , al solutions are st, , issolved in liqu, 1 be used to pre, , ge in liquid, , 2. The alkali met, 3, Ammonium salts d, mistry. They car, y for solvolysis ts le, mmon, , i eparative che’ : E, pa ammonia than t, , 4. The tendenc, Disadvantages of Liquid Ar ja asa Solvent cameane, 1. The liquid range for liquid ammonia is from 43.3° to 77., , x ‘ i i a ia., high pressure Is necessary while working with liquid ammont, Steve hand " i fore, it requires speci, 2. Liquid ammonia has an offensive odour, therefore, juire, , ion medium., , Therefore, a low temp, al techniques to, , a solvent and as a reacti ;, ; : all the reactions are to be carrie, , 3. Liquid ammonia is hygroscopic in nature. Hence,, , sealed tubes., , Which out of NH, of H,0 undergo more autoionisation ?, , @ Ans. H,0, , 5: Complete the foll, , () Pbl, + KNH,, , (i) Hgl, + KNH, i,, ii) $O,Cl, Mi,, (iv) Zn(NH,), + KNH, ee;, , 6. How do the following solutes behave in am:, @) KNH, i) NH,NO,, @ Ans. (i) base (ii) acid., , ——, , PRACTICE, , Problems, , , , , lowing reactions :, NH3, , monia as an acid or base ?, , ae, , ——, , LIQUID SULPHUR DIOXIDE, , Liquid sulphur dioxide is a non-protonic so, any hydrogen atom. It is also one of the important no:, in industry., , Under normal conditions of temperature and ioxide i i, , Under no’ n 1 ‘ pressure, sulphur dioxide is a gas but, readily liquefied and is easily maintained in the liquid phase. it has a wide auld tide (, ci C) and can be used asa solvent. It can be easily purified by passing the gas through s', ; ae > eaessenen $0? a through P,O, to remove traces of water. Its dielectric co, , 1 (15, C) and therefore, is a good solvent for covalent rad, physical properties of liquid sulphur dioxide are given in Table ran =o, , Table 5. Some important physical properties of liquid SO., a, , Ivent or aprotic solvent because it does not, n-aqueous solvents and has been widel, , , , , , , , , , meee Value, , one i, , ey aa Te a —10°C), , Dielectric constant ree,, , ae ta:, conductance (ohm=! em=!) i. 10-8 (at -10°C), , , , Structure of Sulphur dioxide Molecule, , Electron diffraction studies have shown that sulp, , structur 3 amas 9, eas shown ahead. hur dioxide in gaseous phase has the

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SOLVENTS, , , , valence bond theory predicts that the SO, mol i ; 1, resonating structures : 2 molecule is a resonance hybrid of the following, i, , A =f§, , solubilities of Compounds in Liquid Sulphur dioxide, Amongst the inorganic compqunds, iodides and thi st soluble. In case of alkali, , seal halides, the so! ubilities are in the order : MI > MBr > MCI > ME. The uninegative polyatomic, _are generally more soluble in liquid $O,. Salts of multinegative, , snions such as SO,--, SO,2-, S*, O* etc. are practically insoluble, Many of the ammonium, thallium, , and mercuric salts are soluble., Itis an excellent solvent for covalent compounds. Many covalent substances like halogens,, , inter halogens (IBr, ICl etc.), phosphorus halides (PCL,, PBr, etc.), oxyhalides of sulphur, phosphorus, OCI, SOCL,) etc. and halides (CCly SiCly SnCly GeCl, etc.) are soluble in it. Metals are insoluble, , inliquid SO,., Amongst the organic compounds, aromatic hydrocarbons and alkenes (bonded compounds), y in liquid SO, in comparison to saturated hydrocarbons (alkanes). Pyridine,, en derivatives and acid chlorides also dissolve in liquid SO,., | Many compounds dissolve in liquid SO, due to solvate formation. For example,, KL4SO,, Cal,.4S0,, KSCN.SO,. Many donor molecules also form stable solvates with SO,. For, example, C,H;N. SO, C,H,OCH; - $0,, BF; - SO, etc., Autoionisation of SO,, f electricity, though it is believed to autoionize as, , Pure SO, is a poor conductor 0, , |, , , , , , , , , have very high solubilit, | quinoline, ethers, halog', , 250, <> SO" + 90, The thionyl ion SO™) is analogous to the hydronium ion (H,0*) and ammonium ion (NH,*), 2-) corresponds to hydroxyl (OH-) and amide (NH,~) ions of the aqueous and, , and sulphite ion (SO. 1, ae eer syatems respectively., | Reactions in Liquid Sulphur dioxide, Some important chemical reactions in liquid sulphur dioxide are discussed below :, , 1. Acid-base reactions, Liquid SO, undergoes autoionisation as :, F : 280, === so* + SO,, According to solvent system concept of acids and bases, the com) i i, ; ; Sa ( / pounds which give, tion - *) in solutions of SO, would behave as acids, whereas compounds giving itphite, ions (SO,~) in quid SO, would act as bases. For example compounds such as SOC1,, SOBr, et, as acids‘in liquid SO,. : > SOBr, etc., , SOL EEO Sur sort) +: acl, Thionyl chloride - 2, , pe oa