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... ... middle of paper ... ... 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.
It was learned that changing the volume of the same substance will never change the boiling point of the substance. However having two different substances with the same volume will result in two different boiling points. The purpose of this lab was to determine if changing the volume of a substance will change the boiling point. This is useful to know in real life because if someone wanted to boil water to make pasta and did not know how much water to
Mixed melting point was used to confirm the identity of the product. The smaller the range, the more pure the substance. When the two substances are mixed; the melting point should be the same melting range as the as the melting range obtained after filtering. If the mixed melting point is lower one taken from the crystals, then the two substances are different.
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.
3. Why are the crucible and lid heated at the beginning of the experiment before being weighed?
The heat makes the molecules in the mixture expand and move slower than when they are in colder temperatures (source 1). The molecules are like people when it comes to how they react to heat and coldness. When the molecules are cold, they like to be very close to one another and the molecules move fast because they are “shivering” (source 2).This is just a one of many examples and comparisons that I am going make throughout this paper. Some of the examples will be very cheesy. I am going to give a warning. When the molecules are hot, they like to be far apart from one another (source 1). They even might start to sweat like humans, too. The molecules have some energy too, but the molecules just do not have as much energy when they are hot. They like to be lazy like many humans do in hot weather (source 1).
8. Continue stirring. Record the temperature at which crystals begin to appear in the solution.
Then, placing the thermocouple in the test tube to monitor the temperature by the labQuest. After a couple of readings of the solution in the hot bath, the test tube with the thermocouple inside it, should be transferred to the ice bath to monitor the temperature for a fixed length of time while the reading still running. This method should have been performed for all the trails with no additives for the trail
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 experiment is to identify and understand reactions under kinetic and thermodynamic control. A reaction under kinetic and thermodynamic control can form two different types of products. A reaction under kinetic control is known to be irreversible and the product is formed quickly. A reaction under thermodynamic control is known to require rigorous conditions. It is also reversible. The final product is more stable than the product made by kinetic control. The chart below shows the two types of reaction coordinates:
The purpose of the lab was to show the effect of temperature on the rate of
Introduction: A phase change is a result from the kinetic energy (heat) either decreasing or increasing to change the state of matter (i.e. water, liquid, or gas.) Thus saying, freezing is the phase change from a liquid to a solid which results from less kinetic energy/heat. Also, melting is the phase change from a solid to a liquid which results from adding kinetic energy/heat. So, the freezing and melting point of something is the temperature at which these phase changes occur. Therefore, a phase change will occur when a vial of 10 mL of water is placed into a cup of crushed ice mixed with four spoonfuls with 5 mL of sodium chloride for 30 minutes. If 10 mL of water is placed in an ice bath, it will then freeze at 5 degrees Celsius because the kinetic energy will leave quicker with the ice involved. The purpose of this lab is to observe what temperature the water must be to undergo a phase change.
...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.
Cengel, Y. A., & Boles, M. A. (2011). Thermodynamics: An engineering approach (7th ed.). New York, NY: McGraw-Hill.¬¬¬¬
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.