The Effect of Temperature and Concentration on the Rate

Evaluation Like any tryation, there were a bend of potential mistakes during the procedure of the experiment. Errors could graduation exercise arisen as a result of the uncertainties associated with the instruments I utilize to take mensurations, and also as a result of errors associated with the veritable method. Of course, due to the limitations of the procedure, they could not be eliminated completely, so I will develop what I did to annul them to an pleasant level and how I could pack fall in my method to reduce them even further. Equipment justificationThe following table shows the reasons for my choice of equipment in carrying turn off my method. Equipment Justification blow cm3 buret I needed to accurately dance step out large quantities of total heat peroxide (90 cm3 and cl cm3). The c cm3 burette is a precise instrument and would anyow me to mea for certain out the hydrogen peroxide by filling it fewer successions than I would need to with 50 cm3 bure tte. 50 cm3 burette I needed to repeatedly total out underage playscripts of ascendants AI. The burette make the labour convenient, and it is a precise instrument. 250 cm3 volumetric flaskfulful I needed to prevail up a specific volume of a standard solution. The volumetric flask has a low error. 100 cm3 volumetric flask I needed to make up a specific volume of a standard solution. The volumetric flask has a low error. Top pan out sleep I needed to accurately weigh out smallish issue forths of solid when making up my solutions. 25 cm3 Mohr pipette I used the pipette to accurately transfer sulfuric acid when making up solutions. I could not do this with a volumetric pipette, as the volume I transferred was 20 cm3. Distilled body of piddle supply I used the distilled water supply to wash off out any glasswargon and storage jars before using them to empty contamination. Crushed ice I used the ice to cool my reactants bring to 10 C. Water tubful I used the wat er bath to heat my reactants up to 30 C, 40 C and 50 C. It unbroken the temperature constantit does not cool down like hot water in a beaker. Thermometer I needed to measure the temperature of the reactants before pour them into the beaker and stirring them. Magnetic stirrer I used the stirrer to regard the reply mixture was uniformly mixed.This was necessary to produce sharp deform changes. stopwatch I used the stopwatch to understand the quantify of the discolor changes. These are the hold dears I needed to investigate the payoff of temperature and submergence on rate. Measurement errors These are the errors associated with the equipment I used when weighing out solids, measuring volumes of liquid, recording the temperature of my reactants, and recording the times of the gloss changes. Equipment Error 100 cm3 burette 0. 2 cm3 50 cm3 burette 0. 1 cm3 250 cm3 volumetric flask 0. 3 cm3 00 cm3 volumetric flask 0. 2 cm3 25 cm3 Mohr pipette 0. 1 cm3 Top pan balance 0. 005 g Thermometer 0. 5 C Stopwatch 0. 005 s (for instrument), 0. 5 s (for measurements), 0. 05 s (for measurements at 50 C) The stopwatch could record to 2 d. p. but the times I save were affect by my reply time. Recording to 2 d. p. would be pointless, as I could not record that precisely. I decided to record the times to the hot secondly, except for my results at 50 C, where I recorded them to 1 d. p. because of the slight duration of time between the colour changes.Percentage uncertainties Using the measurement errors, I can work out the percentage uncertainties for my measurements. I can do this using the formula percentage uncertainty = error / value of measurement x 100% I made multiple measurements with many of the instruments I used. For these measurements, I will find the uncertainties for three of the values (the highest, the lowest and nonpareil close to the average) to give an indication of how the uncertainty changed across the range of measurements I made. Equipmen t Error Measurement Percentage uncertainty / % 100 cm3 burette 0. cm3 150 cm3 (I used the burette twice, so 0. 4 / 150 =) 0. 27 90 cm3 0. 22 50 cm3 burette 0. 1 cm3 10. 00 cm3 1. 0 5. 00 cm3 2. 0 1. 00 cm3 10 250 cm3 volumetric flask 0. 3 cm3 250 cm3 0. 12 100 cm3 volumetric flask 0. 2 cm3 100 cm3 0. 20 25 cm3 Mohr pipette 0. 1 cm3 20 cm3 0. 50 Top pan balance 0. 005 g 26. 75 g 0. 02 10. 7 g 0. 05 0. 85 g 0. 59 Thermometer 0. 5 C 50 C 1. 0 30 C 1. 7 10 C 5. 0 Stopwatch 0. 5 s 437 s 0. 11 95 s 0. 53 1 s 50 0. 05 s (at 50 C) 31. 8 s 0. 57 12. 9 s 0. 388 1. 5 s 3. 3 The percentage uncertainties varied wildly depending on the error of the instrument and the value of the measurement. The largest uncertainty (50%) came from the stopwatch when I used it to record a time of 1 s. However, this would not have affected my calculations to a great extent, as I only used the time to cast the blue cycle for the first oscillation. It would not have affected the value I calcu lated for the average oscillation period by a pregnant amount, and would not have noticeably affected the trends in my graphs.This applies to all uncertainties from the stopwatch. I could have recorded all my times to 1 d. p. to mitigate the accuracy of my calculations and draw graphs that showed a trend closer to the true one. The second most significant uncertainty (10%) was for the burette when I used it to work 1 cm3 of solution to different try on tubes in order to test the belief of changing the stringency of propanedioic acid, manganese(II) sulfate(VI) and sulfuric acid. This is a very significant error that could have definitely weakened the accuracy of my results.It might explain, for instance, the wildly varying number of oscillations I observed for tests at 0. 01 M manganese(II) sulfate(VI), as well as the change magnitude appearance of anomalous results at trim duckings. Even the uncertainty for a measurement of 10 cm3 using the burette was 1%, which is signific ant. In order to reduce the instrumental error, I could have used a 1 cm3 pipette or syringe to measure very small volumes of solution. I could not have done much more to conveniently transfer larger volumes of solution (i. e. p to 10 cm3) succession reducing the error, as even a 10 cm3 pipette has the same error as a 50 cm3 burette, and it would have been highly time-consuming to transfer my solutions to test tubes using a 1 cm3 pipette. Still, a 1% uncertainty would not have dramatically affected my results. some some other source of significant percentage uncertainties was the thermometerat every temperature the uncertainty was supra 1%. At 10 C, it was 5%, which is particularly significant. This means that I could have instigateed stirring the reactants at a temperature between 9. 5 C and 10. 5 C.However, there were no thermometers more precise than 0. 5 C, so there is not much I could have done to reduce this error. Anyway, looking back at my raw results, the times I recor ded for tests at 10 C were not particularly discordant in comparison with the results I obtained for the other temperatures. All other errors were below 1%, so were insignificant. I used the volumetric flasks correctly, using a Pasteur pipette to add the distilled water for the last centimetre below the graduation augury, checking the mark at eye level in order to make sure I stopped at the correct point.I took readings from the bottom of the meniscus at eye level when using the Mohr pipette and burettes to reduce parallax error. I had to twist up the mass of manganese(II) sulfate(VI)-1-water I weighed on the top pan balance from 0. 845 g to 0. 85, so an 4 d. p. analytical balance would have been better for this, but I did not have access to one. Procedural errors These are the errors that could have arisen from the method and improper technique. When making up solutions, it is important to lave out the glassware and other equipment with distilled water before use.This was partic ularly indispensable for the BR reaction, due to its high sensitivity to chloride ions. As mentioned in my method, I did wash out all equipment with some distilled water before set them in contact with any reactants to minimise the risk of contamination. It would have been insurmountable to continue a small amount of solution from being broken when transferring them. When transferring from a beaker through a funnel to volumetric flask, the small amount left would have led to a lower final concentration then planned. I minimised this error by washing out the beaker with distilled water three times.When pouring solution from the test tubes into the reaction beaker, a small amount is also lost. However, the amount left would have little effect on the results because it is a systematic error, i. e. it is repeated every time the solution is poured. I always inverted the volumetric flasks when making up solutions in order to ensure homogeneity. Before pouring them into the burettes, I gave the storage bottles a swirl in case the uniformity of the solution had been affected during storage. This would prevent the trials from being tested at different concentrations, which would have compromised the accuracy of my results.In addition, I used a magnetic stirrer to make sure the consent of the solution remained even within the reaction beaker. This also meant that the colour changes were sharper. It was peculiarly important that the blue colour change was sharp, as this is the value I used to calculate the oscillation period, and therefore, rate of reaction. However, because human reaction time is not perfect, there was always some delay between the colour change and the pressing of the stopwatch. This is why I could not record times accurate to 2 d. p.At higher temperatures, i. e. 40 C and 50 C, the water from the solutions in the test tubes evaporated a lot faster than at elbow room temperature while being heated in water bath, which would have step-upd the co ncentrations of the reactants and overstated the effect of the temperature increase. I minimised this error by removing the test tubes from the water bath as soon as possible after the temperature of the reactants reached the suppress level. Next time, I would seal the test tubes using stoppers to prevent any water vapour from escaping.Unfortunately, the reactants could not remain at their starting temperature while being stirred, as they had to be poured into a beaker and set on a magnetic stirrer. This means that during tests at 30 C, 40 C and 50 C, the reactants cooled down at 10 C, the reactants warmed up. This would have understated the effect of temperature on rate. There was a problem with the hydrogen peroxide in the burette. Because it was stored in the fridge, it was cold when I took it out. As it warmed up, there were discernible increases in the level of solution in the burette.Trials that were run near the start of the session may have used colder, more concentrated h ydrogen peroxide, which would have affected the rate of reaction. I only took the temperature of reactants when I tested the effect of temperature. In order to resolve this problem next time, I would take out the hydrogen peroxide at the very start of the lesson and wait for it to warm up while setting up the other burettes, magnetic stirrer etc. and also take the temperature of the reactants when testing concentration to see if it might have had a secondary effect on the rate.The potassium iodate(V) was not soluble enough to make Solution F (potassium iodate(V), 0. 5 M). Although I did manage to fully dissolve it with the aid of heat, a small amount crystallised out of solution after it cooled down, which would have decreased the solutions concentration and affected the results I obtained for the tests where I changed the concentration of potassium iodate(V) and sulfuric acid. Next time, I would change the experiment and run the tests at lower concentrations. Reliability My results were quite reliable, as I ran the reaction three times at each temperature and concentration.The number of oscillations was ordinarily the same at each temperature/concentration and the times were concordant to an acceptable degree. There were a few anomalous runs, which I mentioned in my depth psychology section, and gave a possible explanation for above. I could have repeated the experiment a further time when I got inconsistent results, e. g. 0. 01 M manganese(II) sulfate(VI), to increase reliability. Extending the investigation The observations I made about the colours during particular runs were whole qualitative.I could broaden the scope of my investigation by using colourimetry to obtain a quantitative measurement of the colour intensity when the reaction was especially conk or dark. I could then compare it to values from the standard reaction to reinforce my observations. I could also use the data logger to measure the times of the colour changes. I could then compare th e results from this technique to those from the stopwatch and evaluate the advantages and disadvantages to both methods, and decide which one would be better at producing accurate results.Conclusion Overall, I am satisfied that I have made valid conclusions about the effect of temperature and concentration on the rate of the BriggsRauscher reaction. Although I did not fully meet my aim of finding the order of reaction for every reactant, I did discover that the reaction was not typical in this sense, and that the orders of reaction could not easily be found. I did manage to disengage parts of the mechanism through the qualitative observations I made.