EXPERIMENT 4: KINETICS OF THE PERSULFATE-IODIDE CLOCK REACTION

7etermining the Activation Energy, Ea In getting the activation energy, Ea plot 93?>: vs 93?#: and use the combined

e0uation of e0uations  and 

lnK =lnA −

Ea  R ( x )

1

, where x is e0ual to

. Arrange

T 

− Ea the e0uation and the slope obtained from the graph will be e0ual to

('gure  +a&le for Act'6at'o0 E0ergy Computat'o0

 R

 .

('gure  Graph of l0 , 6s l0 B+4 8.00 f(x) = - 5793.48x + 25.82 R² = 1 7.50

ln K  7.00

Linear ()

6.50 0.0031 0.0031 0.0032 0.0032 0.0033 0.0033 0.0034 1/T

2.

A0s9ers to uest'o0s a. 5hat 's the order of the react'o0 '0 terms of sod'um persulfate a0d '0 terms of potass'um 'od'de 5hat 's the o6erall order of the react'o0 - 5ased on the data gathered and computed results the slope from the graph

of sodium per sulfate is 31.= which is also the order of the reaction with respect to sodium per sulfate. And the slope from the graph of potassium iodide is 1.*=1 which is also the order of the reaction with respect to iodide. Adding the two the over-all order of the reaction based on the experiment was 33.&*. #he computed over-all order of the reaction is far  from the theoretical value which is &. #heoretical values with respect to  potassium iodide and sodium persulfate are both 3. &. Comme0t o0 the effect of the reduct'o0 '0 'o0'c stre0gth o0 the rate of react'o0 a0d determ'0e 9hether the reacta0ts 9h'ch form the act'6ated comple1 ha6e charges of the same or d'ffere0t s'g0.

-

"ne factor that can affect the rate reaction is the charges of ions in the reactants presents in the sample solution. #he charges of ions are also related to its ionic strength. #he product of the charges of the ions can indicate if the rate of the reaction would increase or decrease. /hen the  product is positive an increase in the rate would be expected and if the  product is negative a decrease would be expected. If it is neutral, then there will be no changes observed on the rate of the reaction.

c. *de0t'fy sources of error '0 the e1per'me0t a0d est'mate the'r mag0'tude. - Errors may be caused due to contamination of the sample solutions. #he

 potential causes of the contamination are the chemical reagents may not  be properly sealed in the storage, students who get their sample return the excess back to the container again, and also there are students who directly put their instruments into the container of the chemical reagents. 2*.

Co0clus'o0 a0d recomme0dat'o0s: 6onclusion$ #he experiment successfully demonstrated the reaction between iodide and

 persulfate. /hen iodide reacts with persulfate ions, the reaction produces iodine and sulfate. #he iodine produced is immediately consumed by the added thiosulfate ions, and the excess iodine, which the thiosulfate failed to consume, causes the sample to change its color from clear to blue. #he amount of the thiosulfate that is added to the solution indicates how much iodine was produced through the time taken by the reaction to turn blue. "n the other hand, the experiment for the rate constant k, also shows that it is affected and have direct relationship with temperature. 5ut there is an exception

when !ero activation energy is observed. 7uring this circumstance the temperature does not affect the rate constant of the reaction.

@ecommendations$ It is recommended to start from the last solution to check if a change in color will occur within 1 minutes time span. If no changes are observed, adustment on the concentration of the persulfate is advised. If the mixture changed its color upon the addition of solutions 9a: and 9b: to solutions 9c: and 9d:, a decrease in the amount of  9;H:&)&"* solution and increase of the amount of ;a&)&" solution by 3 m2 is advised. Also it is recommended to make sure that the apparatus that you will be using are clean.

2**.

Refere0ces: a. AndrB . "liveira and @oberto 5. Caria 9&118:. D#he chlorate-iodine clock

reactionD. . Am. 6hem. )oc  b. "xford Fniversity 9&11:. G>inetics of the ersulfate-iodide clock reactionG c. 7enes arga et.al. 9&131:, Complex Kinetics of a Landolt-Type eaction: The  Later !hase of the Thiosulfate-"odate