Heat of Mixing: Ethanol and Water

Topics: Thermodynamics, Entropy, Energy Pages: 3 (1034 words) Published: November 9, 2009
Heat of Mixing: Ethanol and Water
The temperature change when known amounts of water and ethanol were mixed was determined to see the enthalpy change in an isothermal and isobaric environment. Agreeable data was found compared to similar experiments. As the mole fraction increased of the solution so did the enthalpy until a certain limit of about 0.32. Since water’s structure and unique properties affect many aspects of a solution, the solutions enthalpy’s decreased at a certain time due to ethanol’s non-electrolyte nature. Introduction Johnson and Oatis (1) state that entropy is one of many reasons why a substance dissolves into another. Since nature tends to go towards a more random state, entropy is a significant factor. Other forces such as neutralization and changes in volume also play a role. As long as change in Gibbs free energy is negative a solution will be formed. An interest in the change of temperature of alcohol when dissolved in water is examined to determine the bonding interactions between ethanol and water. The interactions can either produce heat or absorb heat depending on many factors including a few mentioned before. Theory Since an adiabatic system cannot be attained, heat calibrations are utilized by using known amounts of electrical energy into the solution and observing temperature rise. The electrical energy was found as follows assuming V is voltage and R is resistance: Qmix can then be put into a ratio form with equations 1 and 2 to produce: Another challenge arose since temperature change is affected by many factors which can leak heat in or out of the system. To overcome these challenges the temperature was taken over a period of 6 minutes total (2 before the mix, 2 during the mix, and 2 after the mix). This is to obtain a linear plot with small changes to determine the ΔT values. One last problem arose and that is temperature change must be measured very accurately. A thermistor was used...
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