expt 12- 19

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LECTURE NOTES: Reduction- Oxidation Titration (Expt. 12- 19) 1. Neutralization- acid and base 2. Redox- reducing agent, oxidizing agent Oxidizing agents: KMnO 4 ; ceric sulfate; Iodine ; bromine; potassium iodate Reducing agents: Oxalic acid; ferrous sulfate; sodium thiosulfate Note: h= no. of electrons gained or lost depending on its role in redox

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Expt 12- 19

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BEVERAGE SUSPENDING AGENT

LECTURE NOTES: Reduction- Oxidation Titration(Expt. 12- 19)Neutralization- acid and baseRedox- reducing agent, oxidizing agent

Oxidizing agents: KMnO4 ; ceric sulfate; Iodine ; bromine; potassium iodateReducing agents: Oxalic acid; ferrous sulfate; sodium thiosulfate

Note:

h= no. of electrons gained or lost depending on its role in redox 1EXPERIMENT 12:Preparation and Standardization of Potassium Permanganate Solution2EXPERIMENT 12:A. Preparation of Potassium Permanganate Solution/ Class 1. Weigh roughly 5g of KMnO4 2. Dissolve it in 1500 mL distilled water in a big beaker.3. Cover with a watch glass and boil the solution for 15 mins (prevent evaporation and accelerate destruction of organic matters or decomposition)4. Allow to stand for at least 2 days (allow decomposition of organic matter to proceed to completion)5. Filter through asbestos into an amber color bottle(get rid of decomposition inorganic product which is MnO2, a brown ppt. MnO2 catalyzes the auto decomposition of KMnO4)

3EXPERIMENT 12:LECTURE NOTES:Asbestos- carcinogenic for filtration of inorganic matter should be lined with a glass wool as support (funnel) when used as a filter.

Should be washed with distilled water until water coming out of the funnel is clear before KMnO4 is filtered.

4EXPERIMENT 12:B. Standardization of Potassium Permanganate SolutionWeigh 0.1-0.2g of Na2C2O4 (weighing bottle)2. Dissolve it in 250 mL distilled water in a big beaker.3. Add 7mL of conc. sulfuric acid4. Heat the solution to 70C (maintain ---reaction between sodium oxalate and KMnO4 occurs stoichiometrically in a hot acidic medium)5. Titrate with KMnO4 solution (Geissler) until a light pink color persists for 15 seconds is obtained. ( Geissler: IR, FR)One determination per pairCompute for Mean N and M as a class5EXPERIMENT 12:LECTURE NOTESStandardization: primary standardizationType of Titration: RedoxMethod of Titration: Direct Permanganate method

Na2C2O4 - primary standard, reducing agent

2. KMnO4 -strong oxidizing agent-reacts rapidly with reducing substance in acidic medium- serves as indicator itself due to its intense color imparting a pink coloration -disadvantage: unstable

6EXPERIMENT 12:Lecture Notes3. H2SO4 -to keep the acid conc. constant preventing the formation of MnO2 - supply hydrogen ion

4. Hot acidic medium- the reaction between Na2C2O4 and KMnO4 stoichoimetrically occur in a hot acidic medium.

7EXPERIMENT 12:LECTURE NOTES5. Equation:Molecularlost=1eX 2= 2e x5= 10e +3 +42KMnO4 + 5Na2C2O4 + 8H2SO4 2MnSO4 + 5Na2SO4 + 10CO2 + K2SO4 + 8H2O +7 gained=5e x 2 = 10e +2

Half ionic equation

C2O4 -2 CO2MnO4- Mn+2

Balance the atomsBalance the chargesBalance the number of electrons gained/lost

8EXPERIMENT 12:LECTURE NOTES6. Computation: Normalitymeq KMnO4 = meq Na2C2O4(NxmL) KMnO4 = (g /MEW) Na2C2O4

N KMnO4 = g Na2C2O4 MW h X 1000 mL KMnO4NOTE: h= no. of electrons gained or lost depending on its role in redox KMnO4 (oxidizing agent)= 5 electrons gained Na2C2O4 (reducing agent)= 2 electrons lost

9EXPERIMENT 12:LECTURE NOTES6. Computation: Molarity

mn KMnO4 = mn Na2C2O4 x rr

(MxmL) KMnO4 = (mg /MW) Na2C2O4 X 2KMnO4 5Na2C2O4 M KMnO4 = mg/MW Na2C2O4 X 2KMnO4 5Na2C2O4 mL KMnO4 10EXPERIMENT 13:Preparation and Standardization of Oxalic acid Solution11EXPERIMENT 13:A. Preparation of Oxalic Acid Solution/ Class- Group 5Weigh roughly 9.6g of oxalic acid

2. Dissolve it in distilled water to make 1500 mL

3. Store in an amber colored bottle12EXPERIMENT 13:B. Standardization of Oxalic Acid Solution1. Run down 30 mL of oxalic acid (Mohr) into a big beaker (Mohr : IR, FR)2. Dilute with 200 mL distilled 3. Add 7mL of conc. sulfuric acid4. Heat the solution to 70C (maintain---reaction between oxalic acid and KMnO4 occurs stoichiometrically in a hot acidic medium)5. Titrate with KMnO4 solution (Geissler) until a light pink color persists for 15 seconds is obtained. (Geissler : IR, FR)One determination per pairCompute for Mean N and M as class

13EXPERIMENT 13:LECTURE NOTES

Standardization: Secondary standardizationType of Titration: RedoxMethod of Titration: Direct Permanganate method

KMnO4 secondary standard -strong oxidizing agent-reacts rapidly with reducing substance (oxalic acid) in hot acidic medium- serves as indicator itself due to its intense color imparting a pink coloration -disadvantage: unstable

14EXPERIMENT 13:LECTURE NOTES2. Equation:Molecular

lost= 1ex2 X 5= 10e +3 +42KMnO4 + 5H2C2O4 + 3H2SO4 2MnSO4 + 10CO2 + K2SO4 + 8H2O+7 gained = 5ex2= 10e+2

Half ionic equation

C2O4 -2 CO2MnO4- Mn+2

Balance the atomsBalance the chargesBalance the number of electrons gained/lost

15EXPERIMENT 13:LECTURE NOTES3. Computation: Normalitymeq H2C2O4 = meq KMnO4

(NxmL) H2C2O4 = (NxmL) KMnO4

N H2C2O4 = N x mL KMnO4 mL H2C2O4

16EXPERIMENT 13:LECTURE NOTES3. Computation: Molarity

mn H2C2O4 = mn KMnO4 x rr

(MxmL)H2C2O4 = (MxmL) KMnO4 X 5H2C2O4 2KMnO4

M H2C2O4 = MxmL KMnO4 X 5H2C2O4 2KMnO4 mL H2C2O4 17EXPERIMENT 14:Assay of Sodium Nitrite18EXPERIMENT 14:Assay of Sodium Nitrite1. Weigh 0.4 to 0.5g NaNO2 accurately2. Dissolve it in enough distilled water to make 100mL in a volumetric flask3. Pipet 10 mL NaNO2 solution (wash pipet first)4. Introduce it into a beaker containing a mixture of: 25 mL KMnO4 (Geissler buret: IR, FR)100 mL distilled water 5 mL conc. H2SO4by immersing the tip of the pipet beneath the surface of the permanganate mixture [prevent the escape of nitrous acid (HNO2)]

19EXPERIMENT 14:Assay of Sodium Nitrite5. Warm the liquid to 40C and allow it to stand for 5 minutes. (to accelerate the oxidation of HNO2 to HNO3)6. Add 25 mL of standard oxalic acid solution (Mohr: IR, FR)- (KMnO4 is decolorized because the oxalic acid was added in excess) 7. Heat to 80C8. Titrate with standard KMnO4 to a light pink end point ( Geissler: IR,FR)9. One determination /pair10. Look for USP specifications for NaNO211. Compute Mean % purity as a class12.Disposition20EXPERIMENT 14:LECTURE NOTESAssay of Sodium NitriteType of Titration: RedoxMethod of Titration: Residual Permanganate methodNaNO2- reducing agentKMnO4 oxidizing agent

Note : Ferrous, Calcium, Lead (II) and titanium compounds are also assayed by permanganate method

21EXPERIMENT 14:LECTURE NOTES2. Equation:Molecular

2NaNO2 + H2SO4 2HNO2 + Na2SO4

lost= 2e x5= 10e +3 +55HNO2 +2KMnO4+ 3H2SO4 5HNO3+ 2MnSO4+ K2SO4+ 3H2O +7 +2 gained= 5e X2=10e

lost= 1ex2 X 5= 10e +3 +42KMnO4 + 5H2C2O4 + 3H2SO4 2MnSO4 + 10CO2 + K2SO4 + 8H2O +7 gained = 5ex2= 10e +2

22EXPERIMENT 14:LECTURE NOTES2. Equation:Half ionic equation

NO2- NO3-MnO4- Mn+2

C2O4 -2 CO2MnO4- Mn+2

23EXPERIMENT 14: LECTURE NOTES3. Computation: Normalitymeq NaNO2 = meq KMnO4 that reacts with NaNO2

gpure NaNO2= [(NxmL) Total KMnO4 - (N x 25mL) H2C2O4] MW hx1000

g pure NaNO2= [(N x mL) Total KMnO4 -(N x 25mL) H2C2O4] x MW h x 1000

% NaNO2(w/w) = g pure NaNO2_______X 100

0.4 to 0.5g = X (aliqout) 100 mL 10 mL

24EXPERIMENT 14: LECTURE NOTES3. Computation: Molaritymn NaNO2 = mn KMnO4 that reacts with NaNO2 x rr

gNaNO2= [(MxmL) Total KMnO4 - (M x 25mL) H2C2O4 X KMnO4 ] X HNO2 X NaNO2 X MW H2C2O4 KMnO4 HNO2 1000

gNaNO2= [(M x mL) Total KMnO4 -(M x 25mL) H2C2O4 X 2 KMnO4 ] x 5HNO2 X 2NaNO2 x MW 5 H2C2O4 2KMnO4 2HNO2 1000

% NaNO2(w/w) = g pure NaNO2 X 100 0.4 to 0.5g = X (aliqout) 100 mL 10 mL\

25EXPERIMENT 15:Preparation and Standardization of Sodium thiosulfate Solution26EXPERIMENT 15:LECTURE NOTESExperiment 15-18:Type of Titration: RedoxMethod: Iodimetry/ IodometryIodimetry- is the process wherein a standard solution of iodine is the titrating agent and it acts as an oxidizing agent.

Pharmaceutical solutions assayed Iodimetrically:Arsenites6. ascorbic acidSb+3 compds7. methenamineThiosulfatesSulfitesMercurous compds

27EXPERIMENT 15:LECTURE NOTES2. Iodometry- is a process where in the sample of an oxidizing agent is made to liberate an equivalent amount of iodine from KI which is titrated with Na2S2O3 solution.

Pharmaceutical solutions assayed Iodometrically:Iron6. arsenous2. Copper 7. chlorine3. Manganese8. Bromine4.Chromium9. Iodine5. Cobalt

28EXPERIMENT 15:A. Preparation of Starch SolutionTriturate 1g of arrowroot starch with 10 mL of distilled water. (starch paste)

2. Boil 200 mL of distilled water3. Add the starch paste to it with constant stirring4. Boil the mixture gently until it forms a thin, translucent liquid.29EXPERIMENT 15:LECTURE NOTESStarch test solution- serves a indicator

Starch grains contain:- amylose (water insoluble)- with Iodine forms a violet color-amylose (water soluble)- with Iodine forms blue color30EXPERIMENT 15:LECTURE NOTESLarger grains- arrow root and potatoes( will give more - amylose)

2. Smaller grains- rice and corn ( will give lesser - amylose)

31EXPERIMENT 15:B. Preparation of Sodium Thiosulfate Solution/ Class1. Weigh roughly 26 g of sodium thiosulfate and 0.4 g of sodium carbonate (preservative to prevent acid catalyzed hydrolysis)

2. Dissolve this in 1000 mL of recently boiled and cooled distilled water (for bacterial sterilization and to expel CO2)

3. Store in an amber colored bottle and label.32EXPERIMENT 15:C. Standardization of Sodium Thiosulfate SolutionWeight accurately 1.1g of primary standard KIO3 into a 500-mL volumetric flask;

2. Dissolve in about 200 mL of distilled water. Dilute to the mark and mix thoroughly.- (one per class)3. Pipet 50.0 mL aliquot of standard KIO3 solution into a 250 mL conical flask ( one per paired groups)4. Introduce 2g of KI (iodate free) and swirl the flask to speed up solution.

33EXPERIMENT 15:C. Standardization of Sodium Thiosulfate Solution5. Add 2 mL of 6M HCl (do not add if not Na2S2O3 is not yet ready)- catalyze the liberation of I2

6. Immediately titrate with sodium thiosulfate until solution is pale yellow (reduction of the amount of Iodine)

7. Introduce 5 mL of the starch solution (There will be a formation of big lumps of the blue iodo starch complex if the indicator is added before the titration with Na2S2O3 to the pale yellow endpoint. This will result to difficulty of the blue color to disappear.)

34EXPERIMENT 15:C. Standardization of Sodium Thiosulfate Solution8. Continue the titration with standard sodium thiosulfate to the disappearance of the blue color.

9. One determination per pair10. Compute the Mean N and M of Na2S2O3 as a class

35EXPERIMENT 15:LECTURE NOTESStandardization: primary standardizationType of Titration: RedoxMethod of Titration: Iodometry

1. KIO3- primary standard (oxidizing agent)2. Na2S2O3 titrant; reducing agent

36EXPERIMENT 15:LECTURE NOTES3. Equations:Molecular: +5 gained=5eX2= 10e 0

2KIO3+ 10 KI + 12HCl 6I2 + 12KCl + 6H2O -1 lost= 1 x2=2eX 5= 5e 0 reduced to lowest term: +5 gained = 5e x2= 10e 0 KIO3 + 5KI + 6HCl 3I2 + 6KCl + 3H2O -1 0 lost= 1 x 2=2e X5= 10e

37EXPERIMENT 15:LECTURE NOTES3. Equations:Molecular: +5 gained=5eX2= 10e 0

KIO3+ 5 KI + 6HCl 3I2 + 6KCl + 3H2O -1 lost= 1 x2=2eX 5= 5e 0 0 gained = 1x2=2e X 1= 2e -1 I2 + 2Na2S2O3 2NaI +Na2S4O6 +2 +2.5 lost= 0.5 x 2=1e X2= 2e

38EXPERIMENT 15:LECTURE NOTES3. Equations:Half- ionic equation: IO3- I2 I- I2

S2O3-2 S4O6-2

I2 I-

39EXPERIMENT 15:LECTURE NOTES3. Equations:Half- ionic equation: IO3- + 5 I- 3I2+ 3H2O

2S2O3-2 + I2 S4O6-2 + 2I-

40EXPERIMENT 15:LECTURE NOTES4. Computation: Normalitymeq Na2S2O3 = meq KIO3(NxmL) Na2S2O3 = (g /MEW) KIO3

N Na2S2O3 = g KIO3 MW h X 1000 mL Na2S2O3

Note: g= 1.1g = x 500 mL 50mLh=6

41EXPERIMENT 15:LECTURE NOTES4. Computation: Molarity

mn Na2S2O3 = mn KIO3 x rr

(MxmL) Na2S2O3 = mg KIO3 x 3 I2 x 2Na2S2O3 MW 1 KIO3 1 I2

M Na2S2O3 = mg KIO3 X 3 I2______ x 2Na2S2O3 MW___ 1 KIO3 1 I2 mL Na2S2O3 42EXPERIMENT 16:Preparation and Standardization of Iodine Solution43EXPERIMENT 15:A. Preparation of Iodine Solution/Class Weigh roughly 14.0g of Iodine crystalsDissolve it in a solution of 36 g KI in 400 mL of distilled water. (KI is a solubilizing agent to increase the solubility of Iodine crystals)Add 12 drops of 6N HCl (neutralized any alkali present in KI)Add enough distilled water to complete the volume to 1000 mLStore in an amber colored bottle.

44EXPERIMENT 16:B. Standardization of Iodine Solution Run down 30 mL of sodium thiosulfate (Mohr: IR, FR)Dilute with 100 mL distilled waterAdd 5 mL of starch solution Titrate with standard iodine solution to a blue color endpoint. (Geissler: IR and FR)One determination per pair Compute Mean N and M as a class.

45EXPERIMENT 16:LECTURE NOTESStandardization: secondary standardizationType of Titration: RedoxMethod of Titration: Iodimetry

1. Na2S2O3 solution - secondary standard; reducing agent2. Iodine titrant; oxidizing agent

46EXPERIMENT 16:LECTURE NOTES3. Equations:Molecular: +2 lost=0.5 x2= 1e x 2= 2e + 2.52Na2S2O3+ I2 2NaI+ Na2S4O6 0 -1 gained= -1x2= 2e x1= 2e

47EXPERIMENT 16:LECTURE NOTES3. Equations:Half ionic :

S2O3-2 S4O6-2 I2 I-1

2S2O3-2 + I2 S4O6-2 + 2I-

48EXPERIMENT 16:LECTURE NOTES4. Computation: Normalitymeq I2 = meq Na2S2O3(NxmL) I2 = (NxmL) Na2S2O3

N I2 = N x mL Na2S2O3 mL I2

49EXPERIMENT 16:LECTURE NOTES4. Computation: Molarity

mn I2 = mn Na2S2O3 x rr

(MxmL) I2 = (MxmL) Na2S2O3 X 1 I2 ___ 2 Na2S2O3

M I2 = MxmL Na2S2O3 X 1 I2 ___ 2 Na2S2O3 mL I2 50EXPERIMENT 17:Assay of Tartar Emetic51EXPERIMENT 17:Assay of Tartar Emetic1. Weigh 0.4 to 0.5g tartar emetic accurately (tared flask)2. Dissolve it in 30 mL distilled water 3. Add 25 mL of saturated solution of sodium bicarbonate (neutralize the HI formed thus preventing a reversible reaction and allowing the reaction to proceed to completion)4. Add 5 mL of starch T.S.5. Titrate with standard iodine solution to a blue color end point. (Geissler: IR and FR)6. One determination per pair7. Compute for the mean % purity of tartar emetic as a class.8. Look for USP/ NF specs9. Disposition

52EXPERIMENT 17:LECTURE NOTES1. Tartar Emetic (KOSbC4H4O6. H2O) double saltReducing agent2. Method of Titration: Direct Iodimetric method3. Equation:Molecular +3lost= 2e- +5 KOSbC4H4O6 + I2 + 2NaHCO3 KO2SbC4H4O6 + 2NaI +2CO2 +H2O 0 gained= 1x2= 2e -153EXPERIMENT 17:LECTURE NOTES3. Equation:Half ionic

Sb +3 Sb +5

I2 I-154EXPERIMENT 17:LECTURE NOTES4. Computation: Normality

meq KOSbC4H4O6. H2O = meq I2

(g /MEW) KOSbC4H4O6. H2O = (NxmL) I2

g pure KOSbC4H4O6. H2O = (NxmL) I2 X MW h X 1000

% KOSbC4H4O6. H2O= g pure KOSbC4H4O6. H2O x 100 g impure or g sample

55EXPERIMENT 17:LECTURE NOTES4. Computation: Molarity

mn KOSbC4H4O6. H2O = mn I2 x rr

g pure KOSbC4H4O6. H2O = (MxmL) I2 x 1 KOSbC4H4O6. H2O MW 1 I2 1000

gpure KOSbC4H4O6. H2O = (MxmL) I2 x 1 KOSbC4H4O6. H2O X MW 1 I2 1000

% KOSbC4H4O6. H2O (w/w) = g pure KOSbC4H4O6. H2O X 100 g impure or g sample

56EXPERIMENT 18:Assay of Cupric Sulfate57EXPERIMENT 18:Assay of Cupric Sulfate1. Weigh 0.4 to 0.5g cupric sulfate accurately (tared iodine flask)2. Dissolve it in 50 mL distilled water 3. Add 4 mL of 6 N acetic acid 4. Add 3 g of KI (Note the color change after adding: reddish brown color indicates plenty of I2 is liberated) 5. Titrate the liberated iodine with sodium thiosulfate until a golden yellow color is obtained. ( Mohr: IR) (indicates the reduction of the amount of I2)6. Add 3 mL of starch T.S. (There will be a formation of big lumps of the blue iodo starch complex if the indicator is added before the titration with Na2S2O3 to the golden yellow endpoint. This will result to difficulty of the blue color to disappear.)

58EXPERIMENT 18:Assay of Cupric Sulfate7. Continue the titration with std. sodium thiosulfate solution until the disappearance of blue color. (FR)

8. One determination per pair9. Compute for the % purity of cupric sulfate as a class.10. Look for USP/NF specs11. Disposition59EXPERIMENT 18:LECTURE NOTESAssay of Cupric sulfate 1. CuSO4.5H2O (oxidizing agent)blue vitriol2. KI (reducing agent)

3. Type of Titration: Redox

4. Method of Titration: Iodometry

60EXPERIMENT 18:LECTURE NOTES5. Equations:Molecular+2 gained= 1e X2 =2e +12CuSO4.5H2O +4KI 2CuI + I2 + 2K2SO4 +10 H2O lost= 1e x2=2e X1= 2e

0 gained= 1ex2=2e x1= 2e -1I2 + 2Na2S2O3 2NaI + Na2S4O6 +2 lost= 0.5 X2= 1e X2=2e +2.5 61EXPERIMENT 18:LECTURE NOTES5. Equation:Half ionic

Cu +2 Cu +1

I2 I-162EXPERIMENT 18:LECTURE NOTES4. Computation: Normality

meq CuSO4O6. 5 H2O = meq Na2S2O3

(g /MEW) CuSO4. 5H2O = (NxmL) Na2S2O3

g pure CuSO4 5 H2O = (NxmL) Na2S2O3 X MW CuSO4 5 H2O h X1000

% CuSO4. 5H2O= g pure CuSO4. 5H2O x 100 g impure or g sample

63EXPERIMENT 18:LECTURE NOTES4. Computation: Molarity

mn CuSO4. 5H2O = mn Na2S2O3 x rr

g pure CuSO4. 5H2O = (MxmL) Na2S2O3 x 1 I2 __________ X 2 CuSO4. 5H2O MW 2 Na2S2O3 1 I2 1000

gpure CuSO4. 5H2O = (MxmL)Na2S2O3 x 1 I2 __________ X 2 CuSO4. 5H2O X MW 2 Na2S2O3 1 I2 1000

% CuSO4. 5 H2O (w/w) = g pure CuSO4. 5H2O X 100 g impure or g sample

64EXPERIMENT 19:ASSAY OF ASCORBIC ACID65EXPERIMENT 19:A. Preparation of Standard Potassium Bromate/Class- Group 8 Weigh approximately 1.6 g into a 1000 mL volumetric flask.Dissolve the KBrO3 in about 400-mL of distilled water.Dilute to the mark, mix thoroughly. Keep in an amber bottle.

66EXPERIMENT 19:Assay of Ascorbic Acid1. Weigh accurately 3 to 5 vitamins2. Pulverize them thoroughly in a mortar, and transfer the powder to a dry weighing bottle.3. Weigh accurately 0.4 to 0.5 g sample into a dry 250 mL conical flask (with cover)4. Dissolve the sample in 50mL of 1.5 M H2SO4 (freshly prepared; converts BrO3 to Br2); then add about 5g of KBr. ( will produce excess Br2)5. Titrate immediately with standard KBrO3 to the first faint yellow due to excess Br2 (Geissler: IR, FR)

67EXPERIMENT 19:Assay of Ascorbic AcidRecord the volume of KBrO3 used.7. Add 3g of KI and 5mL of starch indicator; back titrate with standard Na2S2O3 to the disappearance of blue color. (titration should be done without delay to prevent the air oxidation of ascorbic acid) 8. Calculate the ave. mass (in mg) of ascorbic acid tablet.9. Two determination /pair10. Compute Mean % purity per pair11. Look for USP specifications for ascorbic chewable tablets12. Disposition

68EXPERIMENT 19:LECTURE NOTES:Assay of Ascorbic Acid

1.Type of Titration: Redox2. Method: Bromination

Applicable for chewable vitamin C (not coated tablets)

The binder in most Vitamin C tablets remains in the suspension through out the analysis. If the binder is starch, the characteristic color of the complex with I2 appears upon the addition of KI

The volume of Na2S2O3 needed for the back titration seldom exceeds a few millimeters.

69EXPERIMENT 19:LECTURE NOTESEquation: BrO3 + 5Br- + 6H+ 3Br2 + 3H2O

+ Br2 + 2 Br- + 2H+ Ascorbic acid (C6H8O6) dehydro ascorbic acid (C6H6O6)

Br2 + 2 I- Br- + I2

I2 + 2 S2O3-2 2 I- + S4O6-2

70EXPERIMENT 19: LECTURE NOTES4. Computation: Normality

meq AA = meq Br2 that reacts with AA

g/MEWAA= g/MEW KBrO3 - g/MEW Na2S2O3

= whole Br2 - xss Br2

gpure AA = [ (NxmL) KBrO3 - (N x mL) Na2 S2O3 ] MW hx1000

g pure AA= [ (N x mL)KBrO3 - (N x mL) Na2S2O3] x MW AA h x 1000

g pure AA___________ = X________________ g sample (0.4 to 0.5 g) ave. wt of 3- 5 tablets

x= amount (g) of AA/ tablet ; convert to mg/ tablet

71EXPERIMENT 19:LECTURE NOTESComputation: Normality KBrO3

NKBrO3 = 2.6g KBrO3 MW h X 1000 1000 mL

Note: h=6

Equation:

BrO3 Br2

72EXPERIMENT 19: LECTURE NOTES4. Computation: Molarity

mn AA = mn Br2 that reacts with AA x rr

mn AA= mn KBrO3 - mn Na2S2O3 x rr

= whole Br2 - xss Br2 x rr

gpure AA = [(MxmL) KBrO3 x 3Br2 - (M x mL) Na2 S2O3 X 1 I2______ x 1Br2 ] MW 1KBrO3 2Na2S2O3 1I2 1000

g pure AA= [(M x mL)KBrO3 x 3Br2 - (M x mL) Na2S2O3 X 1 I2________ X 1Br2] x MW AA 1KBrO3 2 Na2S2O3 1 I2 1000

g pure AA___________ = X________________ g sample (0.4 to 0.5 g) ave. wt of 3- 5 tablets

x= amount (g) of AA/ tablet ; convert to mg/ tablet

73EXPERIMENT 19:LECTURE NOTESComputation: Molarity KBrO3

MKBrO3 = 2.6g KBrO3 MW 1000 1L

74