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Eutectic Composition of Urea and Trans-cinnamic acid

Independent Research Project

Grace Samenuk

Eutectic Point

Purpose

Eutectic Point

Experiment

The two substances chosen are urea and trans-cinnamic acid

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:

Trans-cinnamic acid

A well known eutectic mixture is that of sodium chloride and water. It lowers the freezing temperature, so it is commonly used on roads to aid with snow removal.

Urea

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"

Heats of Fusion

Data

Results:

Discussion

The break points that were determined from each of the runs and plotted against the mole fraction to determine the eutectic temperature and the eutectic point.

Heats of Fusion

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.

Break Points

Mole fraction of the urea against the determined break point temperatures.

References

Sources of error

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

  • The fact that the trans-cinnamic acid was probably older than it should have been.
  • The difficulty in melting the substances
  • The temperature probe not being fully in the mixture when a reading was taken
  • May or may not have created a bomb on one of the runs.
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