The Entropies of Large Ions. The Heat Capacity, Entropy and Heat of Solution of Potassium Chloroplatinate, Tetramethylammonium Iodide and Uranyl Nitrate Hexahydrate

Coulter, Lowell V.; Pitzer, Kenneth S.; Latimer, Wendell M.

doi:10.1021/ja01867a061

Cited by 42 publications

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“…TMA bromideS or the iodide. 9 Other work bearing on When the solid is heated from room temperature, a the dynamic structures of the compounds include discontinuity in the TJ curve occurs near 418°K. studies of their infrared 6 • 7 and Raman 6 spectra.…”

Section: Experimental Procedures and Resultsmentioning

confidence: 99%

On a T1 and T1ρ Study of Molecular Motion and Phase Transitions in the Tetramethylammonium Halides

Albert

Gutowsky

Ripmeester

1972

The Journal of Chemical Physics

110

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The temperature dependences of methyl group and (CHS)4N+ ion reorientations in the tetramethylammonium salts [(CH S )4N+X-where X is CI, Hr, I] were studied by means of the proton spin-lattice relaxation times in the static and rotating frame (1'1 and TIP) ' The 1\ values calculated for the motions are in good agreement with the double minima observed for each compound. Activation energies and frequency factors were obtained for both motions from the temperature dependence of T, in the three salts. Rotating frame spin-lattice relaxation times were also measured over temperatures from 200 to 380 0 K for (CHs)4NCI, giving results in agreement with those for T,. A discontinuity in the T, of (CHs)4NCI was found near 418°K. This led us to make a preliminary DTA investigation with results indicating that a first-order phase transition may occur near 434°K and another definitely at 528± 1 0 K. The appearance of the phase above 434°K is accompanied by a modulation on the free induction envelope which we ascribe to piezoelectric properties. The phase can be supercooled to room temperature and remains for a considerable length of time. INTRODUCTIONThe motions of the tetramethylammonium (TMA) ion in the solid halides have been the subject of several recent NMR investigations. I-a In the most complete study,! the proton linewidths and second moments were measured for TMA chloride, bromide, and iodide relaxation measurements in order to resolve the two motional processes; the DTA was prompted by the unexpected discontinuity in our TI data for the compound. EXPERIMENTAL PROCEDURE AND RESULTSbetween 77 and 4000K. It was found that at the lowest The three TMA halides were obtained from comtemperatures the absorption is "rigid lattice," while mercial sources. The bromide and chloride came from above room temperature there is motional narrowing Eastman Organic Chemicals, Rochester, New York, by over-all tumbling of the TMA cation as well as by and the iodide (99+% pure) from Matheson, Colemethyl group rotation. At intermediate temperatures man and Bell. A quantity of each was dried over there is a region where motional narrowing is produced molecular sieves in a vacuum dessicator for a number of by methyl group rotation. Proton spin-lattice relax-days and then sealed under vacuum in a Pyrex tube. ation time (T I ) measurement on the TMA bromide The chloride was pumped and dried for longer periods yielded a single minimum which was attributed to the than the two other salts due to its stronger hygroscopic combined effects of methyl group reorientation and nature. Our samples were microanalyzed and were molecular tumbling. 2 Rotating frame spin-lattice re-found to be dry and pure. The proton TJ and Tip laxation times (TIp) of the TMA iodide showed the were' measured as a function of temperature between presence of two minima,a but the data were not analyzed 171 and 483°K at a frequency of 2S.3 MHz using the in any detail. apparatus lO and techniques ll • 12 described previously.1° At room temperature, these three compounds are The ...

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Section: Experimental Procedures and Resultsmentioning

confidence: 99%

On a T1 and T1ρ Study of Molecular Motion and Phase Transitions in the Tetramethylammonium Halides

Albert

Gutowsky

Ripmeester

1972

The Journal of Chemical Physics

110

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“…A third-law entropy (49) for K2PtCl6(c) combined with its solubility (4) and heat of solution (49) leads to S2°= 53 cal deg-1 mole-1 for PtCl6-2(aq). Combination of this entropy with the already determined AGt°leads to AH°= -162 kcal mole-1 for PtCl6-2 (aq).…”

Section: B Thermochemistrymentioning

confidence: 99%

Thermochemistry and oxidation potentials of the platinum group metals and their compounds

Goldberg¹,

Hepler²

1968

Chem. Rev.

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“…The molalities of the aqueous solutes and the total ionic strength, I, of the solution are given by eq 3 and 4, where m is the total molality of U02S04. The value muo22+ = am, mgo42-= am + mHig04, mvoiso, -(1 -°dm (3) I -4 am + 3toH2so4 (4) for 7 ±2-2 is estimated using an extended Debye-Hiickel theory, eq 5.8 Using eq 2-5, a can be calculated at any concentration of U02S04 by a method of log 7± --0.5115ziZ2V// (I + 0.3291aV7) + 0.1W (5) successive approximations.…”

Section: Results and Calculationsmentioning

confidence: 99%

Heats of dilution and the thermodynamics of dissociation of uranyl and vanadyl sulfates

Bailey¹,

Larson²

1971

J. Phys. Chem.

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The Entropies of Large Ions. The Heat Capacity, Entropy and Heat of Solution of Potassium Chloroplatinate, Tetramethylammonium Iodide and Uranyl Nitrate Hexahydrate

Cited by 42 publications

References 0 publications

On a T1 and T1ρ Study of Molecular Motion and Phase Transitions in the Tetramethylammonium Halides

On a T1 and T1ρ Study of Molecular Motion and Phase Transitions in the Tetramethylammonium Halides

Thermochemistry and oxidation potentials of the platinum group metals and their compounds

Heats of dilution and the thermodynamics of dissociation of uranyl and vanadyl sulfates

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