Introduction:
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.
Methods:
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 t...
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... lowest temperature where liquid phase is in equilibrium with solid phase.
Phase diagrams are means that can be used to graphically represent the thermal behavior of mixtures by studying the compositions and temperatures at which particular phases exist, equilibrium curves, and the eutectic point. The diagram has composition on the x axis and temperature on the y-axis at a specific pressure. The equilibrium curves are the phase boundaries of the system. All the systems system studied were at constant pressure, so according to Gibb's Phase rule the degree of the freedom of the system in this case is F = 1 + C - P = 3 - P. Therefore, there is a maximum of 3 phases present in the binary system. At the eutectic point, all 3 distinct phases are in equilibrium consequently the degree of the freedom of the system is now F = 3-3 = 0. In sum, the eutectic point is fixed.
The procedure of the lab on day one was to get a ring stand and clamp, then put the substance in the test tube. Then put the test tube in the clamp and then get a Bunsen burner. After that put the Bunsen burner underneath the test tube to heat it. The procedure of the lab for day two was almost exactly the same, except the substances that were used were different. The
Hess’s Law is also an important concept in this lab. It states that the enthalpy of a reaction is independent of the steps it takes to go from reactant to a product. It happens because enthalpy is a state function. A state function depends on the initial and final state but not the actual process. The Hess’s Law is used to calculate the heat formation of Magnesium Oxide. The amount of heat necessary to create one more mole of a substance is called the Enthalpy of Formation.
For this experiment you have to have a basic understanding of Collision Theory to understand what’s going on in the experiment. Collision Theory is a model of chemical reactions in which a reaction occurs after a collision containing enough energy occurs between two reactant molecules. This model has five factors which can be affected and they are the nature of reactants, temperature, concentrations, surface area and catalyst. If one of these were changed then the reaction could occur faster or slower depending on what was changed.
Moreover, the temperature will witness a decrease after certain amount of time, as the temperature of the solution will decrease to that of the surroundings after peaking. This experiment is also deemed to be exothermic, as energy will be released in the process. Thus, the change in enthalpy will be negative. The graph will also have increasing points, a peak, and a gradual decrease.(The graph will be used to
In a Styrofoam cup, record the temperature of the 200 ml of cold water. This is 200 g of water, as the density of water is 1 g/ml.
The purpose of the lab was to show the effect of temperature on the rate of
When the reactivity of a metal increases, they react more vigorously and thus more heat is released during a reaction. Therefore, the enthalpy change value will be greatest during the reaction between copper sulfate and magnesium since it is the one with the greatest reactivity between the other four metals. Thus it is hypothesized that as the reactivity of different metals begins to increase the absolute value of enthalpy change is expected to increase as
In a 100ml beaker 30mls of water was placed the temperature of the water was recorded. 1 teaspoon of Ammonium Nitrate was added to the water and stirred until dissolved. The temperature was then recorded again. This was to see the difference between the initial temperature and the final temperature.
Methodology: A plastic cup was filled half way with crushed ice and mixed with four spoonfuls of 5 mL of sodium chloride. A thermometer was quickly placed inside the cup to take the temperature and the
Thermodynamics is the branch of science concerned with the nature of heat and its conversion to any form of energy. In thermodynamics, both the thermodynamic system and its environment are considered. A thermodynamic system, in general, is defined by its volume, pressure, temperature, and chemical make-up. In general, the environment will contain heat sources with unlimited heat capacity allowing it to give and receive heat without changing its temperature. Whenever the conditions change, the thermodynamic system will respond by changing its state; the temperature, volume, pressure, or chemical make-up will adjust accordingly in order to reach its original state of equilibrium. There are three laws of thermodynamics in which the changing system can follow in order to return to equilibrium.
These phases can go from one to another when affected by certain things, which is known as phase changes. To switch from a solid to a liquid, the solid must melt. On the other hand, to switch from a liquid to a solid, freezing must occur. Furthermore, to switch from a liquid to a gas, a process known as evaporation must take place. In contrast, to go from a gas to a liquid, condensation must take place. Furthermore, sublimation must take place for a solid to turn to a gas. Inversely, deposition must occur for a gas to change to a solid.
... model for the thermodynamics and fluid mechanics calculations for this system need to be presented.
On further cooling the χT curve shows a sudden increase to 1.23 cm3.K.mol-1 at T=21 K followed by a sharp decrease down to 0.71 cm3.K.mol-1 at 5 K. The χT maximum de...
Next Dalton’s law of partial pressure is used. The mixture of gas in the graduated cylinder was filled with two things: water vapor and air. Using the Dalton’s law, it can be concluded that the total pressure is equal to the pressure of air and the pressure of water vapor added together. This is an endothermic reaction which means that it absorbs heat, and when a reaction gains heat, it is repres...
...pplied to phase quantification only if structures of all phases are known. At the same time still a direct method, an internal standard method and relative intensity ratio (RIR) method are used. It should be noted that each of the available methods has its intrinsic limitation, so that final choice should be made based on specific task and material to be analysed.