Ahmad, Md Faiz

Thakur, Lambodar

English

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NOTESHeats of Solution of Uranyl Nitrate Dihydratein Methanol & EthanolLAMBODARTHAKUR* & MD FAIZ AHMADDepartment of Chemistry, Bhagalpur UniversityBhagalpur 812007Received 8 May 1977; accepted 5 June 1977The heats of solution of UO.(NO.) a-2H.O(c) in metha-nol and ethanol arc -34·3 and -19.3 KJ mol-t, res-tively at 303°K. The heats of solution of UO.(NO")2'2CH30H(c) in methanol and UO.(N03).2C.HsOH(c)in ethanol are -11·7 and -15·8 KJ mol-t, respectively.The standard heats of formation of UO. (N03h.2CH30H(c) and UO.(N03) a- 2C.H.OH(c) are -1935·4 and-1993'2 KJ mol-t, respectively. The mean bonddissociation energies between uranium and oxygen(alcohol) bonds are 77,8 and 72·9 KJ mor-', respectively.THE two water molecules in uranyl nitrate di-hydrate D02(N03)2.2H20 are coordinated touranium forming uranium-oxygen bonds in thetrans-position to the two bidentate nitrate groups'.D02(N03)2.2H20(C) dissolves completely in methanoland ethanol and the solution on evaporation yieldscrystalline uranyl nitrate bis-alcohol, D02(N03)2'2ROH(c), where R is the alkyl radical", In thepresent study we report values for the heats ofsolution of U02(N03)2.2H20(C) in methanol andethanol, of U02(N03)2.2CH30H(c) in methanol andof U02(N03)2.2C2H50H(c) in ethanol. The standardheats of formation of U02(N03)2.2CH30H(c) andU02(N03)2.2C2H50H(c) have been calculated anduranium-oxygen (alcohol) bond strength estimated.Uranyl nitrate hexahydrate (BDH, AR) wasdesiccated over 70% H2S04 for 3 days to formuranyl nitrate trihydrate which on further dehydra-tion over cone. H2S04 at. room temperature in avacuum desiccator for 7 days3,4 yielded uranylnitrate dihydrate [Found: D, 55·1; N, 6·4. Calc.for U02(N03)2.2H20: U, 55·3; N, 6·5%). Thecrystalline dihydrate when dissolved in pure anddry methanol or ethanol, prepared fresh gave aclear greenish-yellow solution which on evaporationunder reduced pressure and at ice-temperatureyielded crystalline uranyl nitrate bis-methanol-ethanol, U02(N03)2.2ROH [Found: D, 49'3; N,6·01. Calc. for U02(N03)2.2CH30H: U, 51'9; N,6·11%. Found: U, 50·4, N, 5·68. Calc. for U02(N03)2.2C2H50H: U, 48·9, N, 5·8%].Uranium was analysed by the oxinate methodand nitrogen by the Duma's method. Attemptsto prepare similar adducts with isopropanol failedas the dihydrate is spraingly soluble in this solvent.The heats of solution were measured in a closed-system calorimeter+", The temperature sensingTABLE 1 - HEATS OF SOLUTIONOF URANYL NITRATEDIHYDRATEANDURANYLNITRATEbis-ALCOHOLIN METHANOLAND ETHANOL AT 303°K(Values in KJ mol")Compound Weight Cone. AH. AHs(g) MSOLVENT:MeOH(I) (125 ml)0-94560 0·017592 -34·31·26285 0·023490 -34·31·27620 0'023740 -33'7Av = -34'4±0'22H O(c)EtOH (125 ml)0·48640 0·009048 -19.41·13830 0·021177 -19·41'59688 0·029708 -19,3Av = -19'4±0'1MeOH (125 ml)0·54370 0·009496 -12·90·78230 0'013664 -11·40'86005 0·015022 -10-9Av = -11·7±0'3U02(NO,)..2HzO(c)UO.(N03)2-2H.O(c)U02(N03}.·2CH30H(c}EtOH (125 ml)0·2725 0'0044840·6838 0·0112551·0589 0'018496-16·4-15·2-15·8Av = -15'8:i:O'Sclement was a 10 kilo-ohm thermistor and a man-ganin heater was used for electrical calibration.The samples were sealed in fragile bulbs which onrupturing mixed rapidly with the calorimeter liquid.Anhydrous uranyl nitrate is difficult to prepare.An indirect method' employing the following thermo-dynamic cycle has been used for the calculationof heats of reaction of lJ02(NOa)2(c) with alcohol,ROH(l), to form lJ02(N03)2.2ROH(c).In the above reactions, /j.H3 and /j.H5 have beendetermined experimentally and the values arelisted in Table 1. For the heat of reaction of UOz(N03)2(C) with 2H20(l) (Eq. 2), we have used thevalue" -58·6 KJ mol>. The dilution of a largevolume of alcohol containing a small amount ofdissolved uranyl nitrate complex with a smallamount of alcohol would have no thermal influenceupon Mf4 and has, therefore, been neglected. Theheat of solution of water in excess of alcohol hasU02(N03}2(C}+2ROH(l} = U02(NO,}2·2ROH(c); j.111 ••• (1)UO.(NO.}.(c} + 2H20(I) = U02(NO.)2.2H.O(c); f),,11. . .. (2)U02(NO.}2.2H20(c}+mROH(I) = UO.(N03) •. 2ROH [in (m-2)ROH.H.O soln); f)"H. ...(3)U02(N03) s-2ROH [in (m-2)ROH, 2H20 solnl+2ROH(I)= UO.(N03}.2ROH [in mMROH, 2H.O soln]; !:J.H. . .. (4)U02(NO.) •.2ROH(c)+mROH(I) = UO.(NO.)..2ROH [in mROH soln]; f)"Hs .•. (5)UO.(NO.) •.2ROH [in mROH solnl+2H20(I) = UO.(NO.)2.2ROH [in mROH, 2H.O soln); !:J.Ho •.. (6)Hence, !:J.Hl=f)"H.+!:J.H3+!:J.H4-f)"Hs-!:J.Ho •.. (7)-To whom all correspondence should be addressed.823INDIAN J. CHEM., VOL. 15A, SEPTEMBER 1977been interpolated from the data8,9 reported in theliterature assuming that the presence of uranylnitrate bis-alcohol will have no effect on the heatof solution. /::"H6 thus estimated for methanoland ethanol complexes, respectively, are 0·42 and1·5 KJ mol'<. Hence /::"H, for U02(N03)2.2CHaOH(c)and U02(N03)2.2C2H50H(c) are -80·8 and -60,6KJ mol>, respectively.Standard heats of formation of uranyl nitrate bis-alcohols - The heats of formation of the his-alcoholcompounds have been calculated from the relation (8).ll.H,= 'E.ll.H/ (products)-'E.ll.Ht (reactants) ... (8)Thereforell.H/UO.(N03) a-2ROH (e) = ll.H/UO.(N03).(e)+2ll.Hj ROH(I)+ll.H ... (9)By computing /::"H; U02(N03)z(c) from Lange8and /::"H; ROH(l) from Cox and Pilcher!", /::"H;U02(N03)2.2CH30H(c) and /::"H; U02(NOa)2.2C2H5-OH(c) come out to be -1935·4 and -1993·2 KJmol", respectively.The mean bond dissociation energy of uranium-oxygen (alcohol) bond has been calculated fromthe following well-knowrr'! steps (10-14):UO.(N03).(e) +2ROH(I) =UO.(N03).·2ROH(e); MI, (10)U02(N03h.2ROH(c) =U02(N03) a- 2ROH(g); su; (11)UO.(N03)2(C)= U02(N031.(g); sn; (12)2ROH(I)=2ROH(g); 2ll.Hv (13)UO.(N03).(g) +2ROH(g) =UO.(N03).·2ROH(g); MI g (14)where /::"H; and /::"H; are the heats of sublimationof uranvl nitrate his-alcohol and uranyl nitrate,respectively; /::"H", the heat of vaporization of thealcohol; and /::"Hr., is the gas-phase moleculardissociation energy. Whence, /::"Hg= /::"HI+/::"H;-/::"H;-2I::,Hv•As pointed out earlier" the heats of sublimationdata are assumed to be the same for uranyl nitrateand the bis-complexes. Hence I::,Hg, for the his-methanol and bis-ethanol are -155·6 and -145,8KJ mol+; and the uranium-oxygen (alcohol) bond-strength, E(O-U)=,-/::"Hg/2=77·8 and 72·9 KJmol'<, respectively for methanol and ethanoladducts, The values compare well with the alcoholand LlCl, bond strength-! in UCI4.4ROH and withthe uranium-oxygen (water) bond strength reportedearlier12,la. The bond strengths in bis-a1cohol arestronger than the uranium-water bond strengthson account of the electron donating effect of thealkyl groups. It can be seen that the steric effectdue to long-chain ethyl group slightly opposes thepositive inductive effect of the ethyl group producinga lower bond strength in his-ethanol.The authors thank the UGC, New Delhi, forcontingent grant and the award of a JRF to oneof them (M.F.A.).References1. BAGNALL,K. W., The actinide elements (Elsevier, NewYork), 1969, 154.2. COMYNS,A. E., cu«. ta«, 60 (1960), 125.3. CORDFUNKE,E. H. P., The chemistry of uranium (Elsevier,New York), 1969, 124.4. CHERNYAEV, 1. 1., Complex compounds of U1'anium,translated by Israel Program for Scientific Translations,Jerusalem, 1966, 240.8245. SMITH,B. C., THAKUR,L. & ROCH,D. P., Cherny Ind.(1965), 1787.6. THAKUll,L., AHMAD,M. F. & PRASAD,R., Indian J.Chcm., 15A (1977), in press.7. STAVELF.Y,L A. K., MAUKHAM,D. R. & JONES,M. R.,.f. iuorg. nucl, Chem., 30 (1968), 231. .8. LANGE,N. A., Handbook of chemistry, 11th cdn (McGrawHill. ~;cw York), 1974, 9.9. VVAGMANN,D. D., EVANS,vV. H., HALOW,1., PARKER,V. B., BAILEY,S. M. & SCHUMM,R. R., Selected valuesof chemical thermodynamic p·ropcrties, NBS TechnicalNote' 270-1, 1965, 107.10. Cox, J. D. & PILCHER,G., Thermochemistry of organic andorganometallic compounds (Academic Press, London),1970, 200.11. SMITH,B. c., THAKUR,L. & WASSEF,M., Indian J. Chern.,7 (1969), 1157.12. ASHCROFT,S. J. & MORTrMER,C. T., 'Thermochemistry oftransition metal complexes (Academic Press, London).1970, 414.13. VDOVENKO,V. M., SI;GLOBOVA,1. G. & SUGLOBOV&D.HYUK, Y. Y., Radiokhimiya, 5 (1963), 739.Viscosity & Apparent Molal Volume ofPotassium Chloride in Acetone-. Dioxane- &Methyl Alcohol-Water MixturesN. C. DAS & P. B. DASDepartment of Chemistry, S.C.S. College, PuriReceived 13 December 1976; accepted 15 June 1977The viscosity and apparent molal volume of potas-sium chloride in acetone-, dioxane- and methylalcohol-water rnixtures containing 10, 20, 30, 40 and50% (w/w) of the organic components have beenmeasured at 35° and the data analysed in terms ofJones-Dole epuation. The values of the constants Aand B of Jones-Dole equation and the apparent molalvolume have been explained in terms of ion-ion andion-solvent interactions.VISCOSITY and apparent molal volume (~) ofelectrolyte solutions in aquo-organic solventshave been studied with a view to understand ingthe nature of ion-ion and ion-solvent interactionrespectivcly-"!'. The viscosity and apparent molalvolume of KCl in acetonc-, dioxane- and methylalcohol-water mixtures containing 10, 20, 30, 40and 50% of the organic solvent have now been,measured at concentrations <O'lM at 35° ± 0.001 0.KC1, acetone, dioxane and methyl alcohol usedwere of E. Merck; (extra pure) qualities. Puri-fication of the solvents and preparation of mixedsolvents and solutions were carried out as reportedearlier+'. The procedures for viscosity measurementwere the same as described by Prasad et al.13• Thedensity measurements were made by pyknometer(50 ml) with buoyancy correction and the valuesare accurate up to 4 in 106• The concentrationrange was from 0·1 to O·OOIM.The applicability of the jones-Dole equation- isshown by the linear plot of Yj,-l/O versus O. Thevalues of the constants A and B, given by theintercept and slope of the plots respectively aregiven in Table 1. The calculated B values are inacceptable agreement with those obtained fromthese plots.

Heats of Solution of Uranyl Nitrate Dihydrate in Methanol & Ethanol

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Heats of Solution of Uranyl Nitrate Dihydrate in Methanol & Ethanol

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