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Thursday, November 14, 2019
Reaction Kinetics Essay -- essays research papers
Reaction Kinetics: Rate of Reaction Of Tertiary-Butyl Bromide Purpose: The purpose of this experiment is to find the order of t-BB graphically, to find the k (rate constant) at 0˚ C and at room temperature, also to find the Ea (activation energy). Principles: Several different chemical kinetic principles were used in this experiment. The reaction rates of this chemical equation were determined experimentally. This then allowed the reaction mechanisms (i.e. orders of each component, rate constant, etc.). These mechanisms were ultimately determined to be compiled to form a rate law. Rate = k[A]m[B]n      Integrated rate laws are used to determine concentrations of reactants at certain times. However, these integrated equations can only be used after the experimental data is collected. Temperature has an effect on the rates of reactions. Swedish chemist, Svante Arrhenius, discovered that the rate constant of a reaction increased logarithmically in proportion to the reciprocal of the absolute temperature. This is expressed mathematically as: k = Ae-ΔE/RT Method: 100 mL of water/ Isopropyl Alcohol were added to a 250 mL Earlenmeyer flask along with 15 drops of phenolphthalein. A buret was washed with soapy water and rinsed with 0.2 M NaOH. The buret was then filled to 0.00 mL. 2.00 mL of NaOH were added to the flask and it was placed into an ice-water bath.      t-BB was injected into the flask by the lab assistant with this exact time being noted. The exact time was recorded once again when the solution became colorless.      About two mL of NaOH were added to the solution and the time recorded when this became colorless. This was done until seven time readings were recorded. After the 7th addition of NaOH, the flask was removed from the ice bath and placed in a hot water bath for approximately ten minutes. The flask was then removed from the bath and cooled to room temperature. The solution was then titrated to a slight pink color. The volume reading of the burette was equal to the total base added during the experiment.      This experiment was repeated in duplicate at room temperature. CH3     CH3 CH3 - C - Br + H2O CH3 - C - OH CH3      CH3      T... ...found to be the 1/H graphs. This means that the reaction was a simple second order reaction. Rate Constant Calculations: A. (11.90-5.29)/(2687-160) = 2.62x10-3                B. (10.00-4.65)/(191-25) = 3.22x10-2 Activation Energy Calculation: ln(k2 – k1) = -(ΔE/8.314) (1/T2 – 1/T1)                     Ea = -8.312 (lnK2 – lnK1) / (1/T2 – 1/T1)                     = -8.314 (ln 3.22x10-2 – ln 2.62x10-3) / (1/298.15 – 1273.15)                     = 67.3 KJ/mol Conclusion: This reaction was found to be simple second order. The rate constants were 2.62 x 10-3 at 0 degrees C, and 3.22 x 10-2 at room temperature. The activation energy was calculated to be 67.3 KJ/mol. There were no unusual problems encountered during this experiment. Error in data may be due to lack of ability to record times accurately.
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