Chemical equilibrium is a crucial topic in Chemistry. To represent and model equilibrium, the thermodynamic concept of Free energy is usually used. For a multi-component system the Gibbs free energy is a function of Pressure, Temperature and quantity (mass, moles) of each component. If one of these parameters is changed, a state change to a more energetically favorable state will occur. This state has the lowest free energy. When the free energy of all states are equal to each other, the system is at equilibrium. The Heat that is relased or absorbed during a state change absorbed is known as latent heat. For a binary mixture such as durene and naphthalene, the Clausius-Clapeyron equation (cf. Appendix) relates the latent heat of fusion or solidification to the rate of change of melting point with pressure. Also when a mixture is cooled its latent heat changes. Since the molar volume change resulting from state change (i.e liquid to solid) is minimal, phase equilibrium is independent of of pressure and depends only on composition and temperature. Therefore by studying a system at different temperatures and various compositions, it should be possible to observe and predict phase changes in that system.
To complete the binary phase experiment, students first set up the experimental apparatus, which consisted of a stir plate, ring stand, Erlenmeyer flask, ice water bath, and a GLX temperature probe. The temperature probe was set to take a data point every second. A stir bar was added to the ice water bath to ensure a uniform temperature throughout the bath, and thus more uniform cooling of the samples. A beaker of boiling water was set up on a hot plate in order to melt the samples. After adjusting the various settings of the probe, the group calibrated the GLX in the boiling water and ice baths respectively.
Once the initial set up was complete, the group collected the first sample of Durene by placing a test tube in a beaker, tearing this system, and then adding in the appropriate amount of Durene. The group then proceeded to melt the sample in the boiling water. The Durene sample was then placed into the ice water bath, and immediately the temperature probe started. As the sample cooled, the group noted at what time the first signs of crystallization occurred. After the sample cooled to about 45°C the run halted, and Naphthalene was added to the sample by the same process used to acquire the first sample of Durene. While these trials were running and being completed, similar trials were conducted for a mixture that started with a sample of Naphthalene. Durene was added to this sample in the same manner as Naphthalene to the Durene sample. The group followed the provided tables when creating the mixtures for each run.
While the lab procedure called for the experiment to take two weeks the group completed the experiment in one lab period. The group then proceeded to export its data to a flash drive from...