Research topic Investigating orders of reaction andactivation energy for the reaction between potassium permanganate andethanedioic acid using a colorimeter.

Research questionWhat is the activation energy for the reactionof potassium permanganate with ethanedioic acid?Personal engagement and aimThere are widespread skin conditions fromwhich many people suffer, particularly teenagers due to the transition periodthey experience.1One of these conditions is Eczema Dermatitis.2 There are many types ofEczema, one of which is Exudative Eczema.3 As a teenager, I developedan interest in researching the treatments of these skin conditions. I found outthat Exudative Eczema can be treated with potassium permanganate.

4 Moreover, I became moreinterested in the kinetics of potassium permanganate, as kinetics is animportant concept to consider in reactions which takes place to producemedications. In addition, I found out that potassium permanganate is on the WHOmodel list for essential medications,5 which makes it moreimportant to investigate its applications and kinetics.Thisinvestigation’s aim is to find the reaction orders for the reaction of potassiumpermanganate with ethanedioic acid. Afterwards, the information gained will be usedto determine the rate constants for the reaction at different temperatures, so thatthe activation energy can be worked out.Background informationThe activation energy is defined as theminimum amount of energy required for a reaction to occur.

6 For a successful reactionto occur, the collision theory7 states that particles mustcollide in the correct orientation, and with energy that equals or is greaterthan the activation energy. Figure 1SK1 8 illustrates how a transition state is reached when reactants havesufficient energy, and hence products are formed. To carry out asuccessful reaction, we should be aware of its activation energy. This valuecan be found through multiple experimental steps: ?rstly, determining theorders of reaction, which can be defined as the relationship between theoverall rate of reaction and the concentration of the reactants9. This should be done foreach reactant through changing the concentration of one reactant, withoutaltering the concentration of the others, to see its effect on the overall rateof reaction at each concentration. There are two methods to determine the valueof the reaction order: graphically or mathematically.

The trend line on therate-concentration graph, as shownin ?gure 2,10indicates a specific order of reaction. Mathematically, information from table(1)11, 12 can be used to work outthe order of reaction.Table 1:information to calculate the order of reaction for each reactant. Effect on rate when doubling the concentration of a reactant Reaction order for the reactant The rate is the same Zero order The rate doubles First order The rate quadruples Second order  To find the rate equation of a reaction, allreaction orders have to be determined. The rate expression includes the rateconstant (k), which remains constant if the concentration varies, but increaseswhen the temperature increases.13 Hence, different valuesof the rate constant (k) can be determined through carrying out the reactionwith fixed concentrations of the reactants at different temperatures.

Increasingthe temperature causes the particles to collide with energy that equals or isgreater than the activation energy.14 Therefore, successfulcollision will occur, and it can be concluded that higher temperatures causefaster rates of reaction. The values for temperature (T), activation energy (Ea),and the rate constant (k), are incorporated into the Arrhenius equation15 presented below. Theequation can be written in the form y = mx + c, to calculate the activationenergy graphically, as shown below.   ?   A is the Arrheniusconstant SK2 which shows the frequency of the collision and their orientation, Tis measured in Kelvin, and R represents the gas constant (8.31 J.K-1.mol-1).

16, 17 Thus, by plotting agraph from the values of (1/T) on the x-axis and ln(k) on the y-axis, thegradient (m) will be equal to (-Ea/R). The value of m istherefore used to calculate the activation energy Ea.Ehtanedioic acid SK3 (C2H2O4), also called oxalic acid,is a dicarboxylic acid present in many plants and vegetables, and produced bymetabolism in the body.18 It is used as a reducingagent.19 On the other hand, potassiumpermanganate (KMnO4) SK4 is a purple crystalline solid, which is dissolved in water to makepotassium permanganate solution, which is used as an oxidizing agent.20 Potassium permanganate reactswith ethanedioic acid in the reaction presented belowSK5 .212MnO4- + 5H2C2O4+ 6H+? 10CO2 + 8H2O + 2Mn+2Initially,the reaction mixture has a purple color, the color of potassium permanganate.

22 On the other hand,ethanedioic acid is colorless.23 As the reaction proceeds,potassium permanganate gets used up, and the color of the solution changes frompurple to colorless.24 A colorimeter can be usedto observe the rate of decolorization of potassium permanganate, as it measuresthe amount of absorbed light of a certain wavelength through a sample over time.25 Hence, the reaction rateis the rate of decrease in absorbance. The absorbance of a sample, given by the Beer-Lambert lawSK6 SK7 , is:   where: A is the absorbance, Iois the intensity of the light passing through the reference cell for eachwavelength of light, and I is the intensity of the light passing througha sample cell for that wavelength.

26 Thus, in this investigation,Io represents the intensity of the light passing throughdistilled water, which the colorimeter was calibrated with, and Irepresents the intensity of the light passing through the reaction mixture forthe chosen wavelength. The wavelength chosen in this investigationis 565nm, because this is the closest wavelength, provided by the settings ofthe colorimeter, for the range of yellow, the complimentary wavelength of purple(figure 3)27,the color of potassium permanganate.Method justificationThe methodology is a modified version of”investigating the reaction between manganate(VII) and ethanedioate ions” from theRoyal Society of Chemistry.28Quantities and concentrations ofchemicals: for the color change to bedistinguishable, potassium permanganate should always is kept as the limiting reactant,otherwise the reaction mixture will not become colorless because potassiumpermanganate will remain, leaving the purple-pink solution.29 Therefore, theconcentration of potassium permanganate used was 0.005 mol.

dm-3SK8 , which is very low so that the decolorization is efficient and distinguishable.Despite the low concentration used, successful reaction will occur in thiscase, because of the low volumes of reactants utilized due to the limited volumesof the cuvettes used in the school lab (3.5cm3). In this instance, the concentrations of thereactants can be varied by changing the volumes of the reactants. Additionally,distilled water should be used to maintain the surface area of the reactionmixture, because changing the surface area impacts the rate of reaction.30 For sustainabilitypurposes, this method is favored because it involves less consumption ofresources to produce different solutions of the reactants at specificconcentrations to be used in the investigation. The initial volumes of each reactant waschosen to be 1.

5cm3, as the volume of the cuvette is limited to3.5cm3, and as the reaction with these volumes, from previous trials,was seen to occur fast for repeats to be taken, and also slow enough for therate of reaction to be accurately derived. Furthermore, low volumes of potassiumpermanganate will cause the color change to occur too fast. Therefore, volumesof 0.

5cm3 or higher were utilized. 1 mol.dm-3 was theconcentration chosen for ethanedioic acid, because higher concentrations causethe rate of reaction to be too fast to follow.31 On the other hand,successful trials can be achieved when using concentrations lower than this.But considering the number of trials and repeats that should be carried out inthis investigation, the experimental process will be inefficient, due to theslow reaction that will take place.

Furthermore, the maximum time taken for thereaction to be completed was found to be 6 minutes, and therefore the settingsof the data logger was chosen to collect data each 10 seconds for a period of 6minutes.Temperatures:by doing trials, it was observed that 5°C is the lowest possible temperature providedby the ice bath. Additionally, the temperatures at which the reactantsdecompose are: 250oC for potassium permanganate32, and 189.5oC forethanedioic acid.33 These are impossible tobe achieved in a hot water bath.

Therefore, there is no concern of thereactants to decompose when choosing high temperatures. However, for the rateof reaction to be accurately derived, the temperatures chosen should not be toohigh, to prevent the reaction from being too fast to follow, as seen above inthe collision theory. To ?t the given information, 5 temperatures were chosen: 45°C,35°C, 25°C, 15°C and 5°C.

Method to derive rate of reaction: the reaction reaches completion when the reaction mixture becomescompletely colorless, because this is an indication that the potassiumpermanganate has completely reacted. Two methods are available to derive therate of reaction: a stop watch to determine the time required so that the colorchange takes place, and colorimetry. In this investigation, colorimetry was used,because when connecting colorimeters to the data logger interface, results are automaticallyshown, so it is not needed to monitor the color change in the reaction mixture.Further, it is subjective to decide when a color change had taken place, whichcan possibly prevent accuracy and consistency in the data derived from theexperimental work. Hence, it is preferred to use colorimetry. Additionally, bychoosing colorimetry, multiple colorimeters, if possible, can be used simultaneouslyreducing time-consumption when collecting data.1 “Teenageskin issues,” Clinuvel, accessed on Oct.

20, 2017, http://clinuvel.com/mothers-children-skin/childrens-skin/teenagers-13-17-years/teenage-skin-issues.2 “Topteen skin problem – and how to solve them,” WebMD, accessed on Oct 20,2017, https://www.webmd.com/skin-problems-and-treatments/acne/features/top-teen-skin-problems-how-to-solve-them#1.3 “AtopicDermatitis and Eczema”, Patient, accessed on Oct 20, 2017, https://patient.

info/doctor/atopic-dermatitis-and-eczema.4Ibid.5 “19thWHO model list for essential medications,” WHO, published in Apr. 2015,29, http://www.who.

int/medicines/publications/essentialmedicines/EML2015_8-May-15.pdf.6 “Activationenergy and temperature dependence of reaction rates,” Mhhe, accessed onOct.

20, 2017, http://www.mhhe.com/physsci/chemistry/chang7/ssg/chap13_4sg.html.7Ibid. 8Jim Clark, “Energy profiles for simple reactions,” chemguide, lastupdated on Oct.

2013, http://www.chemguide.co.uk/physical/basicrates/energyprofiles.html.9 Jim Clark, “Ordersof reaction and rate equations,” chemguide, last updated Oct. 2013, http://www.

chemguide.co.uk/physical/basicrates/orders.html.10 “Lesson3 Rate Law and Reaction Order,” Slideplayer, last updated 2016, http://slideplayer.com/slide/8124464/.

11Jim Clark, “Orders of reaction and rate equations,” chemguide,last updated Oct. 2013, http://www.chemguide.co.uk/physical/basicrates/orders.html.12 Ibid.

13 Jim Clark, “Rate constants and the Arrheniusequation,” chemguide, last updated Oct. 2013, http://www.chemguide.co.uk/physical/basicrates/arrhenius.

html.14 “Activation energy and temperature dependence ofreaction rates.” Mhhe. Accessed on Oct.

20, 2017. http://www.mhhe.com/physsci/chemistry/chang7/ssg/chap13_4sg.html.15 Jim Clark, “Rate constants and the Arrheniusequation.

” chemguide. last updated Oct. 2013. http://www.chemguide.co.uk/physical/basicrates/arrhenius.html.

16 Ibid.17International Baccalaureate Organization. Diploma program.

Chemistry DataBooklet, last updated on Feb. 2014, 2, http://www.ibchem.com/root_pdf/data_booklet_2016.pdf.18″Oxalic acid,” Pubchem, accessed on Jan.

28, 2018, https://pubchem.ncbi.nlm.nih.gov/compound/971#section=Top.19Ibid.20 VanessaNgan and Staff Writer, “Potassium Permanganate,” DermNetNew Zealand, published in 2006, https://www.dermnetnz.

org/topics/potassium-permanganate/.21Herbert Launer, “The kinetics of the reaction between potassium permanganateand oxalic acid,” Journal of the American chemical society, published onJul. 1932, 2597. http://pubs.acs.org/doi/pdf/10.1021/ja01346a003.22 VanessaNgan and Staff Writer, “Potassium Permanganate,” DermNetNew Zealand, published in 2006, https://www.

dermnetnz.org/topics/potassium-permanganate/.National Centerfor Biotechnology Information. PubChem Compound Database; CID=516875,https://pubchem.

ncbi.nlm.nih.

gov/compound/516875 (accessed Oct. 20,2017).National Center for Biotechnology Information. PubChem Compound Database;CID=516875, https://pubchem.

ncbi.nlm.nih.

gov/compound/516875 (accessed Oct. 20,2017).National Center for Biotechnology Information. PubChem Compound Database;CID=516875, https://pubchem.ncbi.nlm.

nih.gov/compound/516875 (accessed Oct. 20,2017).23 “Oxalic acid,” Pubchem, accessed on Jan. 28,2018, https://pubchem.

ncbi.nlm.nih.

gov/compound/971#section=Top.24 “DEMONSTRATION:reaction of oxalic acid,” Leek High School, accessed on Oct. 29, 2017, www.leekhigh.staffs.sch.uk/science/chemistry/Chim/RRfolder/RRD3.doc.

25 “Colorimeter,”Vernier, accessed on Oct. 20, 2017, https://www.vernier.com/products/sensors/colorimeters/col-bta/.

26Jim Clark, “The Beer-Lambert Law,” chemguide, last updated in May 2016, https://www.chemguide.co.uk/analysis/uvvisible/beerlambert.

html.27International Baccalaureate Organization. Diploma program. Chemistry DataBooklet, last updated on Feb. 2014, 15, http://www.ibchem.com/root_pdf/data_booklet_2016.pdf.

   28 “Investigatingthe reaction between manganate(VII) and ethanedioate ions,” Royal Society ofChemistry, accessed on Oct. 20, 2017, http://www.rsc.

org/learn-chemistry/resource/res00002322/investigating-the-reaction-between-manganate-vii-and-ethanedioate-ions?cmpid=CMP00008124.  29 “DEMONSTRATION:reaction of oxalic acid,” Leek High School, accessed on Oct. 29, 2017, www.leekhigh.staffs.sch.uk/science/chemistry/Chim/RRfolder/RRD3.doc.

30″Rate of reaction 3 – Explosions and catalysts,” BBC Bitesize, accessedon Oct. 20, 2017, http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/chemical_economics/reaction3rev1.shtml.  31 “Speedof reactions,” BBC Bitesize, accessed on Oct.

29, 2017, http://www.bbc.co.

uk/bitesize/standard/chemistry/elementsandreactions/speed_of_reactions/revision/1/.32 “Thethermal decomposition of potassium permanganate and related substances. Part I.Chemical aspects,” The Royal Society of Chemistry, accessed on Oct. 29,2017, http://pubs.rsc.

org/en/Content/ArticleLanding/1971/J1/j19710001821#!divAbstract.33″Oxalic acid,” Pubchem, accessed on Jan. 28, 2018, https://pubchem.ncbi.nlm.nih.

gov/compound/971#section=Top. SK1Is this a correct way of referencing figures? How to add thereference within the textbox? SK2Is this a correct way of writing it? SK3What extra information to include about the acid? SK4What extra information do I have to add about potassiumpermanganate? SK5Can I now mention reduction because I don’t have enough space to addmore information? SK6Is the explanation sufficient? SK7Is the explanation enough? Do I have to add anything else? SK8Is M the same as mol.dm-3?

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