Rainey_Experiment 1

Rainey_Experiment 1 - Experiment 1: Solid-Liquid Equilibria...

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Experiment 1: Solid-Liquid Equilibria in a Two-Component System Author: Ben Rainey Group 2 Section 3, T 2:00 PM – 5:00 PM Partner: Ben Huffer October 5, 2010 Abstract : Two-component systems are common to everyday life. In this experiment, the solid-liquid equilibria of the triphenylmethane-stilbene system were studied. The goal of the experiment was to construct a solid-liquid temperature composition phase diagram for the system. Thermal analysis, through Differential Scanning Calorimetry, was the primary method used to construct this diagram. A Mettler Toledo 910e Differential Scanning Calorimeter was utilized to measure the melting endotherms of triphenylmethane-stilbene mixtures. The data obtained from the 910e DSC was analyzed by constructing a phase diagram for the two-component system, plotting peak melting temperature against mole fraction of stilbene present in each sample. The eutectic enthalpy of fusion was also plotted against mole fraction of stilbene. A linear analysis was performed on the eutectic enthalpy of fusion graph. The composition and enthalpy of fusion for the eutectic mixture of triphenylmethane and stilbene was determined to be 50% stilbene and 5 kJ/mol, respectively. The theoretical calculations in this experiment were based on the assumption of ideal solution behavior. In reality, the actual mixtures tested did not behave as ideal solutions. The eutectic composition is reported with an accuracy of 45% when compared to theoretical composition.
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Experiment 1: Solid-Liquid Equilibria in a Two-Component System I. Introduction The main objective of this experiment was to construct the solid-liquid temperature composition phase diagram for a binary system. The components of the system used were triphenylmethane (TPM) and trans-stilbene (SB). Differential Scanning Calorimetry (DSC) was used to collect data regarding the mixtures. DSC operates on the concept of heat flux. The temperature of the sample and reference are recorded by the 910e DSC. A difference between the sample and reference temperatures signifies a differential heat flow between the sample and the reference. The differences cause peaks to occur in the 910e DSC and these peaks are approximately proportional to enthalpies of fusion. The phase diagram constructed was interpreted using the Gibbs Phase Rule. An equilibrium system of P phases and C independent components has F degrees of freedom: = - + F C P 2 (1-1) Interpretation of the phase diagram was also accomplished using the concept of chemical potential. For two phases in equilibrium, the chemical potentials of a given species are equal in each phase containing that species. For ideal systems in which the activity coefficients of both components in the liquid mixture are close to unity for all compositions, the chemical potential of A in the liquid phase can be expressed in terms of its mole fraction: , = ° , + μA1Tf P μA 1Tf P RTflnXA (1-2) where , μA1Tf P is the chemical potential of liquid A at Tf , the freezing point of A,
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This note was uploaded on 03/08/2011 for the course CHEM 232 taught by Professor James during the Spring '11 term at Clemson.

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Rainey_Experiment 1 - Experiment 1: Solid-Liquid Equilibria...

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