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The procedure follows the one outlined in Shoemaker, Garland & Nibler, 1989.
In a binary eutectic phase system, the two substances that are being analyzed are chosen for similar chemical compositions, and more importantly similar melting points.
This experiment is designed to study to heterogeneous equilibrium between two substances in their solid and liquid phases. Various cooling curves of different mixtures of the two substances will be obtained with the help of a Vernier LabQuest; the break point will be plotted against the mole fraction to determine the eutectic point of urea and trans-cinnamic acid.
Eutectic is defined as “relating to or denoting a mixture of substances (in fixed proportions) that melts and solidifies at a single temperature that is lower than the melting points of the separate constituents or of any other mixture of them”
The ratios of the mixtures were loosely followed from TABLE 1 of the procedure
TABLE 1
Modifications:
Molecular formula C9H8O2
Molar mass 148.16 g mol−1
Appearance White crystals
Density 1.2475 g/cm3
Melting point 133 °C
Molecular formula CH4N2O
Molar mass 60.06 g/mol
Appearance White solid
Density 1.32 g/cm3
Melting point
133–135 °C
Instead of taking a reading every 30 seconds from a thermometer, a Vernier LabQuest with a temperature probe was used to record and plot the temperature seven times a minute.
A sand bath was used instead of a water bath.
heat absorbed by a unit mass of a solid at its melting point in order to convert the solid into a liquid at the same temperature; "the heat of fusion is equal to the heat of solidification"
The eutectic composition that is observed is 0.88 urea/cinnamic acid mixture. The accepted eutectic composition of urea and cinnamic acid is approximately 80:20 ratio.
The following is the known heats of fusion for both substances used, as well as the experimentally determined values.
The eutectic temperature that is observed is 88 degrees C. The accepted eutectic temperature is 101.3 degrees C.
Mole fraction of the urea against the determined break point temperatures.
5th Shoemaker, D., Garland, C., & Nibler, J. (1989).Experiments in physical chemistry. ed., pp. 187-194). New York: McGraw-Hill, Inc.
Della Gatta and Ferro, 1987
Della Gatta, G.; Ferro, D., Enthalpies of fusion and solid-to-solid transition, entropies of fusion for urea and twelve alkylureas, Thermochim. Acta, 1987, 122, 143-152.
Singh and Kumar, 1986
Singh, N.B.; Kumar, P., Solidification behavior of the cinnamic acid-p-nitrophenol eutectic system, J. Chem. Eng. Data, 1986, 31, 406-408.
G. P. Matthews, Experimental Physical Chemistry, Clarendon Press, Oxford, 1985, pp. 46-
48, 52-53.
P. P. Blanchette, J. Chem. Ed., 64, 267-269, 1987