The chemistry of orthophosphoric acid and its sodium salts

Neidig, H. A.; Teates, T. G.; Yingling, R. T.

doi:10.1021/ed045p57

Cited by 7 publications

(9 citation statements)

References 6 publications

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“…The heat of reaction of urea and water can be done by the wellknown coffee-cup calorimeter method (1). About 1 to 5 g of urea will give a measurable drop in temperature if dissolved in 50 mL of H2O.…”

Section: Methodsmentioning

confidence: 99%

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The entropy of dissolution of urea

Pickering¹

1987

J. Chem. Educ.

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The existence of endothermic, entropy-driven chemical reactions is of great theoretical importance, since this fact shows that free energy, not just enthalpy, is the driving force for chemicalchange. Yet there are few illustrative lab experiments. The ideal svstem would he a s i m~l e . s~ontaneous . . . reaction where the e"qui1ihrium lies to the right, and yet there is a clear heat ahsorotion. These conditions are met by the dissolution of urea in water.If the reaction is conceptualized as the AH for the reaction will be the heat of solution, a large positive number (3.3 kcallmol). The AGO can he obtained by considering a saturated solution in which the solid is in equilibrium with the solution. For this condition, the equilibrium constant K will he and this will simplify, given the usual convention of unit activity for the solid, toThen AGO for the reaction will he AGO = -RTlnK where R is the gas constant and T the absolute temperature. From this argument it is easy to determine AGO once the concentration is known. If we make the approximation that AH = AH", then ASo for the dissolution of urea will be given AGO = AH" -TAP or, rearranging ASo = AHo -AG" T The measurement of AH is easy and routine in freshman chemistry ( I ) . To he absolutely correct, we should consider the difference between A H and AH" (the latter for the solution refers to a l-m standard state) and also the heat of dilution. However, for mixtures as dilute as those used here, the effect is negligible.

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Section: Methodsmentioning

confidence: 99%

“…The measurement of AH is easy and routine in freshman chemistry (1). To be absolutely correct, we should consider the difference between AH and AH°(the latter for the solution refers to a 1 -m standard state) and also the heat of dilution.…”

Section: Ah°~ag°tmentioning

confidence: 99%

The entropy of dissolution of urea

Pickering¹

1987

J. Chem. Educ.

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“…Compared to other amine solvent groups, polyetheramine enhances the attack against the copper, which made the first phase unstable. This resulted in the appearance of binary phase CuSe 2 in the early stages of the reaction (at 3 hr); however, it did not appear later, which indicates that the polyetheramine-based reaction was very rapid [50]- [51]. To further investigate the valence states of four ions, XPS analysis was used to examine elements valence states of 3-hr nanoparticles, as shown in Fig.…”

Section: Characterization Of Structure and Morphology Of Cztse Nanopamentioning

confidence: 99%

Effect of Solvent Chelating on Crystal Growth Mechanism of CZTSe Nanoink in Polyetheramine

Wang

Shei

Chang

2015

IEEE Trans. Nanotechnology

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This paper reports on the reaction mechanism of Cu 2 ZnSnSe 4 (CZTSe) nanoink via a solvent-thermal reflux method using copper (Cu), zinc (Zn), tin (Sn), and selenium (Se) powders as precursors and polyetheramine as a reaction solvent. The formation of CZTSe nanoparticles in polyetheramine began with the formation of binary phase CuSe 2 due to the strong catalysis provided by polyetheramine. This was followed by the formation of binary phase ZnSe crystals. In the final stage, ternary crystals of Cu 2 SnSe 3 transformed into well-dispersed nanocrystals of Cu 2 ZnSnSe 4 , which are derived from characterization of XRD, Raman and TEM. The size of the crystals was shown to decrease with reaction time due to the emulsification effect of the polyetheramine epoxy group. Quaternary phase CZTSe firstly appeared at 20 hr, and then the composition of the CZTSe tended to become Cu-poor and Zn-rich over time. The proposed reaction mechanism of CZTSe nanoparticles in polyetheramine presented a distinct phase transformation and suitable time-composition properties, which benefited to further solution-based solar cell application.

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“…Chemical kinetics (5), the solubility product principle (1, 2, 4, 6-9) and chemical equilibria of other kinds (4, 8, 10-14), the concept of activity: all can be the subject of quantitative experiments incorporating gravimetric, volumetric, or instrumental techniques. Thermodynamics can be introduced via such experiments (14), and the study of systems involving complex-ion equilibria is particularly fruitful.…”

Section: Temperature On Lead Chloride Solubilitymentioning

confidence: 99%