Saturday, April 6, 2019

Determination of Heat of Solution Essay Example for Free

mark of Heat of Solution EssayABSTRACTThermodynamic jimmys groundwork be de frontierined apply the Vant Hoff isochore method. This method entails the use of equilibrium systems to determine the stir in enthalpy of the root, which can b link up to the change in internal energy of the solution. The vant Hoff isochore relates the equilibrium constant of a chemical reaction at one temperature to the equilibrium constant of the same reaction at a different temperature, allowing it to be worked discover for all temperatures if it is known for one. The experiment used the solution of toluene and naphthalene to determine the change in enthalpy. The counterspy fractions and the tempterature of recrylstallizations were graphed and the slope was compulsive. From the slope the change in enthalpy was determined to be 3.45J. This implies that energy is absorbed by the system.INTRODUCTIONSolutions are very common in nature and in the chemistry lab. They provide the purlieu in which many chemical reactions occur. Thus, in the chemistry classroom and lab, we are immensely interested in solutions, especially liquid solutions. Solutions are defined as homogeneous mixtures of pure substances in which no presumption or settling occurs. We often think of solutions as liquids, but we can have solutions of materials (alloys), gases (air is a solution of nitrogen, oxygen, carbon dioxide, and a number of other gases), and a combination of states such as liquid and strong metals (amalgams) and liquids and gases (nitrogen in the blood, carbonated beverages). The ease of dissolution is dependent on two factors (1) the change in overthrow or randomness (entropy) of the system and (2) the change in the energy of the process (heat of solution). The process is generally prefer when the degree of randomness increases and the energy of the system decreases (exothermic). When dissolution occur the entropy of the system increases. For example, the ions in crystals are highly o rdered. Once dissolved, these same ions in solution are relatively disordered.When a polymer is dissolved in a solvent, the heat measured is a sum of a polymer-solvent interaction term and a term related to the structure that existed in the straightforward polymer relative to its amorphous liquid state. This latter contribution, termed the residual heat, can have an endothermic contribution due to the fusion of crystalline regions and an exothermic contribution due to the recess of structure in noncrystalline amorphous regions. toluene, formerly known as toluol, is a clear, piddle-insoluble liquid with the regular smell of paint thinners. Chemically it is a mono-substituted benzene derivative, i.e. one in which a single henry atom from the benzene rampartcule has been replaced by a univalent group, in this case CH3. It is an aromatic hydrocarbon that is wide used as an industrial feedstock and as a solvent. Like other solvents, toluene is sometimes also used as an inhalant d rug for its intoxicating properties however, this can potentially cause severe neurological harm.Figure 1 Structure of TolueneNaphthalene, also known as naphthalin, bicyclo4.4.0deca-1,3,5,7,9-pentene or antimite is a crystalline, aromatic, white, solid hydrocarbon with formula C10H8 and the structure of two fused benzene rings. It is best known as the traditional, primary trimmings of mothballs. It is volatile, forming a flammable vapor, and readily sublimes at room temperature, producing a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass.Figure 2 Structure of NaphthaleneEXPERIMENTALA. Compounds testedNaphthalene, TolueneB. ProceduresAn accurate quantity of 15 g of naphthalene was weighed and placed into a test tube. An accurately measured bulk of 5mL of toluene was also added. The stopper, thermometer, and stirrer were fitted in the set-up. The test tube was warmed in a water bath until all the solute was dissolved. The solution was allowed to c ool in air, and was stirred continuously until an appearance of a solid was observed. The temperature at which the solid was observed was also recorded. Warming the mixture until the entire solid was re-dissolved and allowing the solution to be cooled in air also did a second determination. Another 1mL of toluene was added and steps 3 to 5 were repeated. Another four more 1mL portions of toluene were also added. The mole fractions were determined and graphed with the temperature of recrystallization. From the graph, the slope was determined and from the value of the slope, the enthalpy change of the solution.RESULTS AND DISCUSSIONSThe mole fraction of the naphthalene to the toluene was determined and the temperature at which is recrystallized is tabulated belowTable 1 Mole Fraction and temperature of recrystallizationMole fraction Temp.0.45 670.41 600.37 590.34 560.31 560.29 54Besides calorimetric method of analysis, using the equilibrium system may also be utilized to determine th ermodynamic values. This is dependent to the enthalpy change. The mole fraction also interferes with the equilibrium system. Changes in the mole fraction will cause the equilibrium system to shift from one form to another. The process is in isochore, denoting no change in volume. The volume of the naphthalene is not diminished in the process of the experiment. The change in enthalpy is determined by determining the slope of the graph between the inverse of the emperature and the mole fraction.Figure3 interpret of Mole fraction versus the inverse of the recrystallization temperatureFrom the grpah above, there is an inverse relationship between the recrystallization temperature and the mole fraction of naphthalene. As the mole fraction of the naphthalene is decreased, the inverse of the temperature of crystallization is increased. From the slope of the graph, we are able to determine the enthalpy change of the solution. Using the formula Figure 4 Equation for enthalpy changeFrom the equation above the determined enthalpy change is 3.45 J. Since the enthalpy change is a positive value the transfer of energy is towards the system.REFERENCES1 Rossotti and H. Rossotti, The goal of Stability Constants, McGraw-Hill, 19612 Atkins, Peter De Paula, Julio (2006-03-10). Physical Chemistry (8th ed.). W.H. Freeman and Company. p. 212.3 NonLinear vant hoff solubility. http//www.sciencedirect.com/science?_ob=ArticleURL_udi=B6T7W-479CM6F-3M_user=10_coverDate=01%2F31%2F1984_rdoc=1_fmt=high_orig=search_origin=search_sort=d_docanchor=view=c_searchStrId=1474224563_rerunOrigin=google_acct=C000050221_version=1_urlVersion=0_userid=10md5=bc9cac9220a53d018a21b381170d2732searchtype=a. taken kinsfolk 28, 20104 Vant Hoff Isochore. http//www.scenta.co.uk/tcaep/nonxml/science/equations/details/vant%20Hoff%20isochore.htm taken September 28, 2010.

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