INTRODUCTION
This experiment experiment involve redox redox titration titration which is is iodometry.Iodometry iodometry.Iodometry is used used to determine amount of oxidising agent that is standard potaasium iodate(V) solution by titrating iodine and thiosulphate . In this experiment,the experiment ,the standard potassium iodate(V) solution which acts as an oxidising agent is added in excess to acidied potassium iodide solution release iodine.Iodine iodine.Iodine is liberated from iodate and $ $ iodide according to the euation! I" # % &I % '% #I* % #*" . The iodine solution, which is a dar+ brown colour, can be titrated against sodium thiosulfate solution. The sodium thiosulfate thiosulfate solution solution is placed placed in the burette burette and, as it is added added to the conical as+, it reacts with the iodine and the colour of the solution fades. -hen it reaches a light yellow colour, ve drops of a starch solution are added. The solution becomes dar+ blue, and the titration is continued until it goes colourless.The titration reaction represented by the euation! I * % **"#*$ *I$ % /"'*$ .
OBJECTIVES
The ob0ectives of this experiment experiment is to prepare prepare standard standard solution solution of potassium potassium iodate .1urthermore,to determine the concentration of a given sodium thiosulphate solution via iodometric titration. This experiment also help us to have hand$on practice ..2oreover,to +now how to handle the materials,apparatus and the proper techniues of carrying out a titration as well as being careful to avoid any experimental error and accident.3astly, this experiment also to show the correct steps to calculate the concentration concentration of a given sodium thiosulphate solution. APPARATUS
4ropper,5lass 6od,1ilter 1unnel,7ipette 1iller,-eighing 4ish,8ea+er(&9ml),7ipette(*&ml),8urette(&9ml), :nalytic 8alance,;onical 8alance,;onical 1las+(*&9ml),2easuring 1las+(*&9ml),2easuring ;ylinder(*&ml) MATERIALS
tarch olution(<=),ulphuric :cid(<.92),7otassium Iodide(olid),7otassium Iodate(olid),odium Iodate(olid),odium Thiosulphate Thiosulphate olution
METHOD
7art : ! 7reparation of tandard 7otassium Iodate olution <. >sing weighing weighing dish dish and analytical analytical balance, balance, 9.&9// 9.&9// g of potassium potassium iodate iodate is weighed. *& m3 of distilled water is added into &9m3 of bea+er and stirred with a glass rod to dissolve entire solid. *. Through a lter funnel, potassium iodate is lled into into *&9m3 volumetric as+. 8ea+er is rinsed with distilled water and poured into volumetric as+. #. 2ore distilled distilled water water is added added to the volumetric up up to the calibration mar+. 7ut stopper in place and sha+e the as+ until homogenous solution is obtained.
7art 8 ! tandardisation of 9.<92 odium Thiosulphate solution <. 8urette is rinsed and lled with sodium thiosulphate solution. 2a+e sure that there are no air space in the burette. Initial reading of burette is recorded to the nearest 9.9
-e have conducted experiment on redox reaction which is iodometry. Iodometry is the type of titration that uses a sodium thiosulfate solution as the titrant, one of the few stable reducing agents where oxidisation of air is concerned. Iodometry is used to determine the concentration of oxidising agents through an indirect process involving iodine as the intermediary. In the presence of iodine, the thiosulphate ions oxidise uantitatively to the tetrathionate ions. To determine the concentration of the oxidising agents which is standard potassium iodate(V) solution, standard potassium iodate(V) solution is added in excess to acidied potassium iodide solution to release iodine which represent by this euation , I" #$(a)%&I$(a)%'%(a) #*"(l)%#I*(a). This process release iodine and then react with sodium thiosulphate(VI) solution represent by this euation, I* (a) %**"#*$(a) *I$(a)%/"'*$ .:s the solution is mixed with Bl,titrate immediately with the thiosulphate to prevent the iodine from vapourising.
1rom the experiment we conducted,the reaction between the measured gram of potassium iodide and *&.9m3 of potassium iodate solution which produced colourless solution.Then we added sulphuric acid solution which turn the solution into dar+ brown.Cext,the solution is titrated with sodium thiosulphate solution until turn yellowish.-hen the solution turn light yellow,uic+ly add ve drop of starch solution which will turn the solution into dar+ blue.:s soon the dar+ blue appear continue the titration until the solution turn colourless. The result of the concentration of sodium thiosulphate solution in mol 3 $< can be obtain from this experiment.The volume of iodine used is *&.9m3.Then nd the 2oles of I* used.The moles of I * used is wsdwcwdw . 1rom balanced euation!
**"#*$ % I* *I$ % /"'*$ ,we +now that * moles *"#* react < mole I* produced * moles I $ and < mole /"'*$ . Cext,nd the moles of thiosulfate reacting.Therefore,the moles of thiosulfate reacting gfdfdhf.The volume of sodium thiosulfate solution used hasgdhasgas.Then, calculate the molesDm3 of sodium thiosulfate solution.The molesDm3 of thiosulphate solution is gv0gv0gvhgv.Then convert molesDm3 to molesDlitre of sodium thiosulfate solution.The molesDlitre of thiosulphate isadfasfasfa.Therefore,the concentration of sodium thiosulfate solution is sdfaa.
To obtain volume of volume of sodium thiosulfate solution used ,calculate the average volume of sodium thiosulphate used.The titration have to be repeated until two successive results agree to within 9.*9m3.In this experiment we manage to obtain two successive results agree to within 9.*9m3 that is
CONCLUSION
1rom this experiment our ob0ectives is achieved.-e are able to prepare standard solution of potassium iodate . -e also able to determine the concentration of a given sodium thiosulphate solution via iodometric titration.This experiment also teach and help us on the hand$on practice . 1urthermore,through this experiment we able to handle the materials and apparatus correctly.-e also learn the correct way to the proper techniues of carrying out a titration as well as being careful to avoid any experimental error and accident.3astly,this experiment help us to calculate the concentration of a given sodium thiosulphate solution correctly.This experiment also enhance our communication s+ill and teamwor+.1rom our result ,the concentration of sodium thiosulphate is dsgfdsfs.
Post lab
<.-hen mixing potassioum iodate(V) solution to acidied potassium iodide ,the change in oxidation number for iodide ion is from $< to 9. *. olution in the conical as+ must be titrated immediately because Iodine solutions lac+ stability. Iodine is volatile and loss of iodine occurs when it is expose for a short periods.Iodide is also susceptible to air oxidation in an acidic medium which represented by this euation, /I $ % /% % "* *I* % **" .
Nobec aus epot as si um i odi dei s pr es enti nal ar geex c es s.I ti st hepot as si um i odat et hati st hel i mi t i ng #. r e a c t a n t .
/. The starch indicator added near the end point that is when the solution become li+e yellow because to give a sharp end$point, while avoiding the formation of excess starch$iodine complex, which would be diFcult to decompose. &.-e need to do a standardiGation on a +nown concentration sodium thiosulphate solution because to determine the exact concentration of the solution.
6H1H6HC;H 8oo+s Toon, *99&, ;hemistry for 2atriculation emestrer <, 1ourth Hdition, "xford 1a0ar dn. 8hd. hah :lam, *? Internet :rticle :nonymous,Iodometry,retrieved on ' 0une *9<& from https!DDen.m.wi+ipedia.orgDwi+iDIodometry
