FINAL_experiment 8_oxalate in the Sample

 Name: Eldee R. Balolong Student Number: 2007-58545 Class-Section: Chem 28.1-1 Date Performed: September 18, 2008 Date Submitted: September 29, 2008

I.

TITLE. Determination of the oxalate in the sample(experiment 8)

I I.

RESULTS. Standardization of Potassium Permanganate Solution Primary Standard used: Sodium Oxalate O Formula mass of 1 standard: 134.00 g/mol O % Purity of 1 standard: 99.8%

Trials Weight of Na 2C2O4 (g) Corrected Weight Na 2C2O4 (g) Final Reading KMnO 4 (ml) Initial Reading KMnO 4 (ml) Volume KMnO 4 used (ml)

1 0.2862 0.2856 44.80 0.1000 44.70

2 0.2989 0.2983 47.70 1.700 46.00

3 0.2856 0.2850 44.60 0.000 44.60

Corrected Vol. of KMnO 4 mL

44.60

45.90

44.50

 Normality of KMnO 4 Ave. Normality of KMnO 4 Indicator Blank 

Trials Final volume KMnO 4 (ml) Initial volume KMnO 4 (ml)   Net Volume KMnO4 (ml) Ave. volume of KMnO 4 (ml)

1

2 45.0 44.9 0.1

3 45.1 45.0 0.1 0.1

45.2 45.1 0.1

Sample Analysis

Trials Weight of the sample (g) Final volume KMnO 4 (ml) Initial volume KMnO 4 (ml)   Net Volume KMnO4 (ml) Corrected volume of KMnO 4, ml mg Na2C2O4 of unknown % Na2C2O4 of unknown Average % Na 2C2O4 of unknown

1

2 0.5028 39.10 0.1000 39.00 38.90

3 0.5023 38.60 0.1000 38.50 38.40

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III. III.

Samp Sample le Calc Calcul ulat atio ions ns

A. Corrected Mass of Na 2C2O4 (g) Masscorrected=M  Na2C2O4 * 0.9980 Masscorrected=0.2862 g * 0.9980 Masscorrected=0.2856 g

B.  Net Volume KMnO 4 Vnet of KMnO4 =(Vfinal KMnO4)-(Vinitial KMnO4) Vnet of KMnO4 =(44.80 mL)-(0.1000 mL) Vnet of KMnO4=44.70 mL

C. Corrected Vol. of KMnO4

Corrected Correc ted Vol VolKMnO4= Net Volume KMnO4 - Ave. volumeKMnO4 in indicator blank  Corrected Correc ted Vol VolKMnO4=44.70 mL-0.1000 mL Corrected VolKMnO4=44.60 mL

D.  Normality of KMnO 4  NormalityKMnO4=[(corrected weight Na2C2O4/m.w Na2C2O4)] Corrected volume KMnO4  NormalityKMnO4

=

NormalityKMnO4=

E. Average NormalityKMnO4  NormalityKMnO4=(0.1005 M + 0.09970 M + 0.1011 M)/3  NormalityKMnO4=0.1004 M

* for the indicator blank 

F. Net Volume Volume of KMnO4  Net VolumeKMnO4=45.0 mL - 44.9 mL Net VolumeKMnO4=0.1000 mL

G. Average Volume Volume of KMnO4 Average Volume KMnO4=(0.1000 mL + 0.1000 mL + 0.1000 mL)/3 Average VolumeKMnO4=0.1000 mL

**for the sample analysis H. Net volume of KMnO4 Vnet=39.10 mL- 0.1000 mL Vnet=39.00 mL

F. Corrected Vol. of KMnO4

Corrected Correc ted Vol VolKMnO4= Net Volume KMnO4 - Ave. volumeKMnO4 in indicator blank  Corrected Correc ted Vol VolKMnO4=39.00 mL-0.1000 mL Corrected VolKMnO4=38.90 mL

I.

mg Na2C2O4 of unknown mg Na2C2O4=(corrected volumeKMnO4)(Nave KMnO4)(1 mol KMnO 4/ 5 eq KMnO 4)x (5 mol Na2C2O4/2 mol KMnO 4)(m.w. Na2C2O4) mg Na2C2O4

mgNa2C2O4=

 J.

% oxalate in sample % oxalate in the sample= (mg Na 2C2O4/Wsample)*100% % oxalate in the sample =

K. Ave % oxal oxalate ate in in the the sample sample Ave % oxalate=( Ave % oxalate=

IV.

Dis Discus cussion sion

The permanganate ion, MnO4-, is a powerful oxidizing agent; it reacts to form Mn 2+ ion. MnO4- + 8H+ +5e-  Mn2+ + 4 H 2O is the half reaction reaction of Pemanganate to form the Mn 2+ and the one responsible for the color during the endpoint; the Manganese goes from an oxidation state from 7 to 2 thereby saying it has been reduced and is the oxidizing agent in this experiment. Each Permanganate ion will consume 5 electrons to produce the Mn 2+ and it has to be done in ACIDIC medium since the presence of H + marks this type of medium; each MnO 4- will also steal 5 electrons in the sense of it being the oxidizing agent; it will oxidize another species and that is the oxalate.

The Oxalate ion is a stable ion, yet it can be oxidized: C 2O42-  2 CO 2 + 2e-. 2e-. The C in the oxalate has an oxidation state of +5 while the C in CO 2 has an oxidation state of +4; given these oxidation states, each carbon will therefore release 1 electron and each oxalate will release 2 electrons.

o 2MnO4- + 16 H+ + 5 C2O42-

2 Mn+2 + 8 H2O + 10 CO2 (g)

In addition addition to OXALA OXALATE being a strong strong oxidizin oxidizing g agent, agent, permangan permanganate ate has another  important property; it is a compound compound with an intense purple purple color. Even one drop of the titrant is enough enough to produce produce a strong strong pink color. color. With With such property, property, the titration titration process process just goes by titrating until the solution remains pink. The titration process used DRIED sodium oxalate being the primary standard; it has to be dried since the analyst aims to have a compound in its pure form; and no other contaminants or   bound water in them. The procedures encountered required the titer to be heated first in a water bath for 80˚C to 90˚C; of course, water bath is used for the analyst to control the temperature of the system not to exceed that of water even if a thermometer was used. used. The reaction of permanganate tends to to  be relatively slow; it can take 30 to 60 seconds; and this would make the titration relatively impractica impracticall to perform. perform. However However,, the reaction reaction is much faster in the presence presence of a catalyst; catalyst; a catalyst can never AFFECT the final outcome of the titration titration process. In this case, Mn 2+ is a good catalyst. So after the first small addition of of MnO 4-, the reaction will speed up and proceed at a comf comfor orta tabl blee rate rate;; this this is call called ed auto autoca cata taly lysi siss as Mn 2+ is form formed ed in this his reac reacttion AUTOMATICALLY. With the facts established on the slowness of this reaction, one way of speeding up the reaction is through heating the reaction and this is what we done asides from the autocatalysis that happened. As experienced by the 2 analysts, there was a hard time reading the buret because of the color of the titrant which is so strong. As read on some sources with a possible solution to this encountered problem in the experiment, sighting across the top of the liquid is one way; of  course, It is still important that our eye be level with that of the liquid layer to avoid parallax errors. A blank indicator was used in this experiment to have a corrected and expected volume free from other contaminants.

COMMENT: I had problems with the visibility of the grid lines in the buret; the color of the  permanganate solution is one hindrance to a sure shot in reading the buret upon taking volume readings. One thing about this experiment was that the permanganate solution was not EXACTLY EXACTLY diluted to 1 L; this is analytical chemistry therefore even in this simple preparation, we could have somehow approximated it would be near a liter. How about before starting the experiment, a kind of story telling where we are told of the applications of this experiment in day to da y activities and how we could apply this to our  courses; for example, in public health, what could possibly be the applications of this in human systems or maybe in chemical che mical engineering, what could possibly be certain mechanisms we can apply when faced with systems like that.