The 'olution -a' diluted -ith 5)ml pre* oiled -ater and titrated -ith thio'ul/ate 'olution until the ro-n color o/ iodine had almo't di'appeared. ?i+e milliliter' o/ 'tarch 'olution, -hich -a' prepared in procedure @, -a' added and titration -a' continued until the la't drop o/ titrant remo+ed the lue color o/ 'tarch iodine complex i+in a clear emerald*reen 'olution. Three trial' -ere done and the molarity o/ 'odium thio'ul/ate -a' calculated in each. The a+erae de+iation 'hould e %*2ppt. @. 6reparation o/ (tarch Indicator In 5ml pre+iou'ly oiled -ater, ).5 'tarch -a' di''ol+ed. Thi' -a' added to %))mL oilin -ater and -a' oiled /or another # minute'. ". ;naly'i' o/ the Un9no-n T-o milliliter' o/ li0uid leach -a' placed into each o/ #5)mL Erlenmeyer /la'9'. Then, 5)ml o/ pre+iou'ly oiled -ater, 2 =I, AmL o/ %:< 'ul/uric acid and 2 drop' o/ 2B ammonium molydate 4cataly't -ere added to the 'olution. The /la'9' -ere co+ered -ith -atch la''e' and le/t to 'tand /or 2 minute' to alloreaction to complete. The lierated iodine -a' titrated -ith 'tandardied thio'ul/ate 'olution until ro-n color o/ iodine ha' almo't di'appeared. ?i+e milliliter' o / 'tarch indicator -a' added and titration -a' continued until lue color di'appeared. The B "l in each trial -a' calculated -ith the a''umption that the den'ity o/ li0uid leach i' %.) 3mL. V. Results Reaction' In+ol+ed: (tandardiation: 2 %1>4a0"r #O$#*4a0#O4l #(#O2#*4a0 I#4a0 → #I*4a0 (1O<#*4a0 @leachin 6o-er: #>4a0 "lO*4a0#I*4a0 → "l*4a0 I#4a0 >#O4l #(#O2#*4a0 I#4a0 → #I*4a0 (1O<#*4a0 ;. (tandardiation o/ Na#(#)2 (olution Trial &eiht o/ Colume o/ =#"r #O$ Na#(#)2 4 4mL % ).%#)1 ##.5 # ).%12$ %D.% 2 ).%215 #).1
Molarity Na#(#)2 ).%)D%M ).%521M ).%215M
;+erae Molarity Na#(#)2: ).%2#2M "omputation': T%:
"hem #$.% Oxidation*Reduction Titration Iodimetry
4).%#)1= #"r #O$4mol= #"r #O$3#D1.%A5= #"r #O$ 4mol "r #O$#*3mol =#"r #O$42 mol I #3mol "r #O$#*4# mol (#O2#*3mol I#4%3).)##5L ).%)D%M T#: 4).%12$= #"r #O$4mol= #"r #O$3#D1.%A5= #"r #O$ 4mol "r #O$#*3mol =#"r #O$42 mol I #3mol "r #O$#*4# mol (#O2#*3mol I#4%3).)%D%L ).%521M T2: 4).%215= #"r #O$4mol= #"r #O$3#D1.%A5= #"r #O$ 4mol "r #O$#*3mol =#"r #O$42 mol I #3mol "r #O$#*4# mol (#O2#*3mol I#4%3).)#)1L ).%215M @. 7etermination o/ Trial Colume o/ (ample 4each diluted to <)mL % #mL # #mL 2 #mL
@leachin 6o-er Colume B"l in o/ (ample Na#(#)2 4mL #<.% %$.< %A.<
the
).)2)< 3mL ).)#)< 3mL ).)#%A 3mL
;+erae B"l in (ample: ).)#12 3mL "omputation': n, (#O2#*: T%: 4).%2#2M4).)#<%L 2.152)x%) *2 mol T#: 4).%2#2M4).)%$
to the 'olution o/ iodine cau'e' the /ormation o/ the I2* complex in acidic condition', -hich -a' helped alon y 'ul/uric acid. &ithout proper handlin, iodine can e lo't y +aporiation. There/ore, pre+enti+e mea'ure' 'uch a' the co+erin o/ -atch la'' mu't e exerci'ed to pre+ent lo'' o/ iodine. In the 'tandardiation, the molarity o/ the thio'ul/ate 'olution -a' otained y di+idin the -eiht o/ the dried dichromate y the molecular ma'' o/ pota''ium dichromate. The 0uotient -a' then 'toichiometrically con+erted to mole' o/ (#O2#*, and then di+ided y the +olume o/ 'odium thio'ul/ate otained throuh titration. The 'tarch indicator -a' only added immediately e/ore the e0ui+alence point to pre+ent 'ome o/ the iodine /rom remainin ound to the 'tarch particle'. The acti+e inredient in commercial leach i' 'odium hypochlorite, Na"lO, occurrin u'ually a' 2*ypochlorite i' the 'trone't oxidiin aent o/ the chlorine oxyanion' and thi' oxidiin po-er ma9e' them e//ecti+e leache'. In thi' experiment, the leachin po-er o/ the 'ample -a' determined y otainin the molarity o/ "lO* throuh the mole' o/ ( #O2#*. ;/ter computin the molarity o/ "lO *, the concentration o/ "l*, thu' the leachin po-er can e determined. VII. onclusions and Recommendations In thi' experiment, the B"l * o/ the un9no-n leach 'ample -a' determined. It -a' /ound that the a+erae content o/ un9no-n leach -a' ).)#12 3mL. 6o''ile 'ource' o/ error could e the lo'' o/ iodine due to the compoundF' +olatility, air oxidation cau'in chane' in the iodine concentration, timin o/ the addition o/ 'tarch
"hem #$.% Oxidation*Reduction Titration Iodimetry
indicator, in'u//icient acidity o/ 'tandard iodine 'olution', or rea9in do-n o/ 'odium thio'ul/ate prior to titration. ;' it i' -ith e+ery titration method, it i' recommended to ha+e a plain, -hite a'e /or the titration 'etup and al'o, to o'er+e proper laoratory attire 'ince 'ome reaent' are irritant'. (trict o'er+ation o/ proper procedure, 'uch a' the handlin and di'po'in o/ reaent', i' al'o hihly recommended. VIII. Re!erences %.
#.
(9oo, 7.,&e't, 7, >oller, ?., "rouch, (. 4#)%2. ?undamental' o/ ;nalytical "hemi'try Dth Ed. "enae Learnin @roo9'3"ole. United (tate'. "hri'tian, !. 4#))1. ;nalytical "hemi'try
I herey certi/y that I ha+e i+en 'u'tantial contriution to thi' report
Jumalon, Nathaniel John U.
Lacanilao, Miuel
6ae 2 o/ 2
