From the attached lab how did they calculate…
From the attached lab how did they calculate Reaction K’ for each of the experiments? CHM222 Lap Report This is an unformatted preview. Please download the attached document for the original format. Abstract: Background: The rate law is the change in chemical over a change in time. The reaction is based off of the time that it takes for the reaction to occur. The different amounts of chemicals put into each reaction determine how long it will take for the reaction to take place. When it comes to concentration a higher concentration of reactants leads to more effective collisions in time. This in turn leads to an increasing reaction rate with the exception of zero order reactions. A higher concentration of products is more likely to be associated with a lower reaction rate. The increase in temperature is normally accompanied by an increased reaction rate. Temperature is a measure of the kinetic energy of a system therefore, the higher temperature the higher the average kinetic energy of molecules and more collisions in time. Once the temperature reaches a certain point, some of the chemical may become changed and the chemical reaction will either slow down or stop. Catalyst enzymes lower the activation energy of a chemical reaction. They also increase the rate of a chemical reaction without being consumed in the process. They work by increasing the frequency of collisions between reactants, thus altering the orientation of reactants so that more collisions are effective. This reduces the intermolecular bonding within reactant molecules. The activation energy can be determined through the temperature because the drop in the relative rate versus the time is significant. The Arrhenius Equation y=mx+b because temperature is the lnk=lnA?(Ea/kBT) relates to independent the slope variable and the rate constant is the dependent variable, thus replacing with the equation above. The temperature should be plotted on the x- axis and the rate constant shall be plotted on the y- axis. The line will have appeared constant, then appear to drastically decrease then rise again. The clock reaction records the amount of time it takes for each solutions reaction to occur. It helps to create the ratio between the rate of change and the time. The starch indicator allows the solution to show that a reaction is actually taking place. the hydrochloric acid is detected by the starch indicator. Procedure: Results: Dependence of Reaction Rate on Concentration Time t Reaction Relative (sec) for Rate of Reactant Concentrations in Reacting Temp. in ( ? ) C Mixture Reaction Change 1 2 3 4 5 Color to 1000/t 160 76 101 45 193 6.25 13.15 9.90 22.22 5.18 Mixture (M) .0020 .0040 .0020 .0020 .0016 .008 .004 .016 .008 .004 .02 .02 .02 .04 .03 21.0 21.0 25.0 23.0 25.0 Effect of Temperature of Reaction Rate: The Activation Energy 20 Approximate Temperature in C ? 40 10 0 Time in t in seconds 144 58 299 258 21 33 17 12 6.85 1.92 294 1/294 1.78 .576 306 1/306 14.6 2.68 290 1/290 21.5 3.07 285 1/285 for color to appear Temperature of the reaction mixture in C ? Relative Rate = 1000/t Ln of relative rate Temperature T in K 1/T, K Effect of a Catalyst on Reaction Rate Reaction 1 Catalyzed Reaction 1 Time for color to 144 7.8 7.8 appear (seconds) Relative Rate 1= 7.59 = k’ (.002) m (.008) n (.02) p Relative Rate 2= 16.95 = k’ (.004) m (.008) n (.02) p Reaction 1Rate 1/ Relative Rate 2 = (.002)m(.008)n(.02)p4 2 3 K’ave Relative /(.004)m(.008)n(.02)p K’ 3.125 6.575 = log (.5)/ log (.5) 4.95 11.11 3.66 m m=1 m= 1 n= 1 p= 2 Discussion: During the clock reaction the student combined the contents of Reaction Flask I and Reaction Flask II, which contained the two component solutions for the reaction mixture, and observed that after a period of elapsed time. The concentration of the various ions in the solution affected the time in which the color change occurred. When the concentration of [ I- ] ion increased the time for the detected color change was nearly halved. The increase in concentration of the BrO3- ion also resulted in a decreased time, but not to the same degree as the I- ion. Finally, the increase in concentration of the H+ had the most profound decrease in the time required for the color change. These elapsed times translated into higher relative rates with smaller amounts of time and smaller relative rates with larger amounts of time demonstrating the inverse proportionality between reaction time and relative rate. These determined relative rates are crucial to the determination of the rate laws and there order numbers. The students compared Reaction 1 to the Reaction 2, 3, and 4 to obtain the order numbers because Reaction Mixture 2, 3, and 4 only differ from Reaction 1 in concentration of one ion. This ratio of difference was used to find the order numbers to be m=1, n=1, and p=1. With these value known the students were able to predict the relative rate and time for Reaction 5. The predicted relative rate was 5.56 and the predicted time was 180 seconds. This was slightly inaccurate when compared to the observed relative rate of 5.18 and the observed time of 193 seconds. Now in addition to the calculation of the relative rate and order numbers the students also determined the rate constant for each of the performed reactions. To determine this order numbers were input into the formula Relative Rate = k’ (I-) m (BrO3-) n (H+) p and then solved for k’. The resulting constants were, with the exception of Reaction 4, within a close range of one another. This was expected because the solutions were only slightly different from one another. All of this information was used to determine the activation energy of the reaction. This was achieved when the students plotted 1/T versus the ln of the relative rate. Using this graph in conjunction with the Arrhenius equation the activation energy could be calculated by relating the slope and the rate constant of 8.31. This yielded activation energy of 4,615 joules. When compared to the actual value of the 41,400 joules the experiment yielded a percent error of 88 percent. The source of this error came from an erroneous reading and/or preparation of one of 40 degree trial. This caused the slope to be significantly higher than anticipated which resulted in smaller activation energy. Finally, when a catalyst was added to one of the solutions and reacted together the rate of reaction increased dramatically. This was due to the presence of the catalyst which decreased the activation energy required for the reaction to occur. Conclusion: The goal of the project was to find the time it took to for a chemical reaction to take place. The group was somewhat successful in achieving each goal. The rates of the chemical reactions are within the same time frame. The more concentrated the solution, the longer it took for the reaction to take place. The experiment does not need to be improved however, the whole experiment needs to be repeated twice in order to make sure all the results are completely accurate. References Cengage Learning (2000); Signature Labs’ Chemistry Handout; Rate of Chemical Reactions; II. A Clock Reaction; p160-165 General Chemistry; Gilbert, Kirss, Foster, Davies Lab Report 3: Rate Law Experiment Jeneé T. Glover Due: Mar. 21, 2013 CHEM 222L-01 Additional Requirements Level of Detail: Show all work