Analytical Chemistry Laboratory Manual 2
ANALYTICAL CHEMISTRYLABORATORY MANUAL 2Ankara University Faculty of PharmacyDepartment of Analytical ChemistryAnalytical Chemistry Practices
ContentsINTRODUCTION TO QUANTITATIVE ANALYSIS . 2VOLUMETRIC ANALYSIS . 2Volumetric Analysis Calculations . 3Dilution Factor . 4Standard Solutions . 5Primary standard. 5Characteristics of Quantitative Reaction . 5Preparation of 1 L 0.1 M HCl Solution . 6Preparation of 1 L 0.1 M NaOH Solution . 6NEUTRALIZATION TITRATIONS . 7STANDARDIZATION OF 0.1 N NaOH SOLUTION . 7STANDARDIZATION OF 0.1 M HCl SOLUTION . 9DETERMINATION OF BORIC ACID (H3BO3) . 10PERCENT PURITY DETERMINATION OF ASPIRIN SAMPLES . 12CaCO3 PURITY DETERMINATION . 13H3PO4 (PHOSPHORIC ACID) DETERMINATION . 15REDOX TITRATIONS . 18PERMANGANOMETRY . 18Preparation of 0.02 M 1 L KMnO4 Solution . 18Standardization of KMnO4 Solution. 18FeSO4 DETERMINATION. 20IODIMETRY AND IODOMETRY . 21TITRATION WITH IODINE. 21METAMIZOLE SODIUM DETERMINATION . 22COMPLEXOMETRIC TITRATIONS . 23EDTA TITRATIONS . 23Ca2 EDTA TITRATION . 24PRECIPITATION TITRATIONS . 23ARGENTOMETRIC Cl- DETERMINATION . 251
INTRODUCTION TO QUANTITATIVE ANALYSISQuantitative analytical chemistry is related with the quantitative determinations of substances.Today, many methods for quantification exist. In practice, some factors such as the structuralproperties of a material, sensitivity, accuracy, reliability, ease of implementation and costeffectiveness of methods are considered for selecting a proper method. In our lab, volumetricand instrumental techniques will be used for quantitative analysis.Qualitative AnalysisQuantitative AnalysisAnalysis for identification of species in asample.Analysis for determination of the quantitiesof species in a sample.Quantitative Analytical MethodsClassical MethodsInstrumental MethodsIf the analysis is carried out solely usingsolutions of chemical substances, this is calledas classical analysis.- Gravimetric analysis- Volumetric analysisIf the analysis is performed using adevice, then it is called instrumentalanalysis.- Spectroscopic analysis- Electrochemical analysis- Chromatographic analysisVOLUMETRIC ANALYSISVolumetric analysis is a quantitative analysis based on the measurement of the volume ofsolutions that gives reaction. Here, the concentration of analyte can be found by reacting it witha standard solution with a known concentration.The volumetric analysis is based on the stoichiometry between reactive species. For example;A B ABaccording to the above reaction, the stoichiometry between A and B is 1:1. It means 1 mol ofA reacts with 1 mol of B to give 1 mol of AB.C 2D CD2On the other hand, for the above reaction, the stoichiometry between C and D is 1:2. It means1 mol of C reacts with 2 moles of D to give 1 mol of CD2.2
Volumetric Analysis CalculationsA B ABThe concentration of a sample A can be found by reaction with a substance B with exactlyknown concentration (standard solution). Since they reacted 1:1 ratio, their moles will be equalat the end of reaction (equivalence point):nA nBMA x VA MB x VBHere, VA and VB are the volumes of A and B, and MB is the molarity of B. By using thisequation, the molarity of A (MA) can be calculated.For calculation of concentration in g/L, molarity of A can be multiplied with molecular weightof A:C (g/L) MA x MWAIf the mol ratio is different than 1:1, then this must be taken into account. For example, theconcentration of an analyte C can be found by reacting it with a standardized solution of Dwith a mol ratio of 1:2. It means 1 mol of C reacts with 2 moles of D.C 2D CD2In this case, firstly the mol of D should be calculated. If the D is an aqueous solution, then usevolume and molarity of it:ππ· MD x VDIf the D is solid, then use the amount and molecular weight of it.πππ· ππ΄π·π·Then calculate the mol of C that reacts with:2 moles of D reacts with1 mol of Cππ· mol D reacts withx mol of C.Calculate x which is the mol of C and using x calculate molarity of C:π₯ππΆ ππΆFinally, for calculation of concentration in g/L, molarity of C can be multiplied with molecularweight of C:C (g/L) MC x MWC3
Dilution FactorSamples are (not necessarily but generally) diluted before analysis. The reason for dilution maybe the reduction of reagent use in the analysis or increase of the volume of the sample so thatanalysis can be repeated when neccesary. Dilution must be accounted in calculations:Dilution ratio amount before dilution / amount after dilutionDilution factor (DF) amount after dilution / amount before dilutionFor example, if 90 mL of distilled water is added onto 10 mL sample, the total volume afterdilution will be 100 mL. It means that the sample is diluted 10/100 ratio (or 1/10 ratio). Thedilution factor in this case:DF 100/10 10After the titration, the concentration of the diluted sample can be calculated using titrationresults. Then the concentration of the real sample can be calculated by multiplying theconcentration of diluted sample with DF.Example:A concentrated sample of 20 mL HCl is diluted to 100 mL with distilled water. Then 25 mL ofthe diluted sample is titrated with 0.1 M 12.5 mL NaOH. Calculate the molarity of the sample?HCl NaOH NaCl H2O (mol ratio 1:1)The moles of NaOH consumed during titration can be calculated from the following equationusing the volume of NaOH that is consumed in the titration and the molarity of the NaOH.nNaOH MNaOH x VNaOHAccording to the reaction equation:If1 mol NaOH reacts withnNaOH mol reacts with1 mol HClx mol HClFrom this ratio, the moles of HCl (π₯ nHCl ) is calculated and the molarity of diluted HCl iscalculated from x.MHCl π₯VHClThe molarity of the original sample (Mπ πππππ ) then can be calculated by multiplying themolarity of the diluted sample by the dilution factor.Dilution factor 100 / 20 5Msample MHCl x DFMsample 0.05 x 5Msample 0.25 M4
Standard SolutionsStandard solutions are solutions that have exactly known concentration and react with analytes.For example, if concentration of a base solution is to be determined, an acid solution withknown concentration can be used as standard solution.The standard solution can be prepared by precisely weighing the required amount of reagent.Then, the precise concentration of the standard solution can be found by the reaction withspecial substances called primary standards.Primary standardA primary standard is a highly pure compound that serves as a reference material in volumetricand mass titrimetric methods. The accuracy of a method is critically dependent on the propertiesof this compound. Important requirements for a primary standard are the following:1. Highly pure or exact purity must be known.2. Atmospheric stability.3. Absence of hydrate water so that the composition of the solid does not change with variationsin humidity.4. Modest cost.5. Reasonable solubility in the titration medium.6. Reasonably large molar mass so that the relative error associated with weighing the standardis minimized.Primary standards for acid standardization:KHCO3, TlCO3 Na2CO3Primary standards for base standardization:KHC8H4O4, H2C2O4.2H2O, HC7H5O2 .Characteristics of Quantitative Reaction1) Reaction must be specific and unique2) Reaction must be in one direction3) The reaction must be fast4) The end of the reaction can be detected easily5) The reaction must be repeatable yielding same results every time.5
Preparation of 1 L 0.1 M HCl SolutionFrom HCl stock solution, 37% purity, d 1.19 g/cm3m d xVThe weight of concentrated HCl of 1000 mL ism 1.19 x1000 1190 gr.In 100 gIn 1190 g37 g HCl is purexx 440.3 g pure HCl1M1 L HCl36.5 g HCl required0.1 M1L3.65 g HCl requires.1000 mL440.3 g pure HClx3.65 g HClx 8.3 mLTherefore, if you take 8.3 mL acid and dilute it to 1000 mL it will be 1 L, 0.1 M HCl. Do notforget, never add acid to water*, put some water to volumetric flask first, then add 8.3 mL ofHCl. And mix it well, finally complete it to 1000 mL till the line.*If you add water onto acid, then high amount of heat is produced and it may explode!Preparation of 1 L 0.1 M NaOH Solution1L1 M NaOH solution40 g NaOH required2.5 L0.1 M10 g NaOH requires.10 g of NaOH is weighed in watch glasses**. Then it is transferred to a beaker and dissolvedin nearly 400 mL of distilled water. Transfer it to the volumetric flask, complete it until 1 L.Then transfer it to 2.5 L of bottle. Add 1.5 L more distilled water to this bottle and mix well.Do not forget labelling.**Be careful! NaOH is a strong irritant. In case of contact, please wash the affected area withcopious amount of water.6
NEUTRALIZATION TITRATIONSThe reaction between an acid and a base is called as neutralization reaction.Titration is a laboratory technique that measures the concentration of an analyte using reactionbetween analyte and standard solution (solution of known concentration).Acid-base titrations is also called neutralization titrations.Acidimetry is the determination of concentration of basic substances by titration with astandard acid solution, and alkalimetry is the measurement of concentration of acid substancesby titration with a standard base solution.The end-point (equivalence point) of acid-base reactions are observed by using indicatorswhich are substances that changes colors near their pKa. Therefore, a suitable indicator shouldbe selected for acids and bases that are reacted.A titration curve is a plot of pH vs. the amount of titrant added. Shape of titration curves differfor weak and strong acid-bases or for polyprotic acids and bases.Tips for Titrations1) Solutions must be shaken well before starting.2) First, a known volume of the analyte is placed in an erlenmeyer flask, and a few drops ofan acid-base indicator, such as phenolphthalein, are added.3) Next, the standard solution is placed into a burette. This solution is also called as titrant.4) Then, the titrant is added drop by drop to the analyte while swirling the erlenmeyer flask.Titration must be performed slowly and always hold stopcock one hand while swirling theflask with other hand.STANDARDIZATION OF 0.1 N NaOH SOLUTIONExperimental procedure:Carefully weigh 0.1-0.2 gram of oxalic acid (H2C2O4.2H2O) and note the exact amount. Thisshould be done by taking required amount of oxalic acid from the stock of oxalic acid on thebalance and transferring it to an erlenmeyer flask.Dissolve oxalic acid by adding 50 mL of water into the erlenmeyer flask.7
Add 1-2 drops of phenolphthalein to the erlenmeyer flask.Fill a burette with NaOH solution that you want to standardize. Check for leak and bubbles.Read the bottom of the meniscus.Deliver solution drop by drop to the erlenmeyer flask by turning the stopcock while swirlingthe flask. Continue to the titration until the color of the solution in the flask turns to light pink.Reaction equation:H2C2O4 2NaOH Na2C2O4 2H2O(mol ratio in reaction 1:2)Calculations:Firstly, mol of oxalic acid is calculated using weighted oxalic acid.(MWH2 C2 O4.2H2O 126.1 g/mol)nC2 π»2 π4 .2π»2 O mH2 C2 O4.2H2O126.1According to the reaction equation:If1 mol C2H2O4.2H2O reacts withnC2 H2O4 .2H2 O mol C2H2O4.2H2O reacts with2 moles NaOHx mol NaOHFrom this ratio, the moles of NaOH (π₯ nNaOH ) is calculated and the molarity NaOH iscalculated from x.Mππππ» π₯VNaOHWeighing oxalic acid:Take the crucible having oxalic acid in it from desiccator and put it onto a balance.Take a note of the amount on the screen (For example 30.100 g).For taking 0.1 - 0.2 g of oxalic acid30.100 β 0.2 29.90030.100 β 0.1 30.000We need to take an amount of oxalic acid that the remaining amount must be in between 29.900g β 30.000 g.8
If the final amount of remaining oxalic acid is 29,980 then we took30.100 β 29.980 0.120 gramThen, by using a spatula, take required amount of oxalic acid and transfer it to the erlenmeyerflask and keep the spatula in the flask for flushing the oxalic acid sticked on the surface of thespatula.STANDARDIZATION OF 0.1 M HCl SOLUTIONExperimental:Pour 10 mL HCl into an erlenmeyer flask and add 1-2 drops of phenolphthalein.Fill a burette with NaOH solution that you already standardized.Titrate until light pink color.Reaction equation:HCl NaOH NaCl H2O (reaction mol ratio 1:1)Calculations:First, the moles of NaOH consumed during titration can be calculated from the followingequation using the volume of NaOH that is consumed in the titration and the molarity of theNaOH.nππππ» MNaOH x VNaOHAccording to the reaction equation:If1 mol NaOH reacts withnNaOH mol reacts with1 mol HClx mol HClFrom this ratio, the moles of HCl (π₯ nHCl ) is calculated and the molarity HCl is calculatedfrom x.MHCl π₯VHCl9
DETERMINATION OF BORIC ACID (H3BO3)Experimental procedure:Each student receives 5 mL of boric acid solution with different concentrations in a 100 mLvolumetric flask.Complete the sample in the flask to 100 mL with distilled water. Take a portion of it into anerlenmeyer flask with your single volume pipette. Add 10 mL glycerol solution (1:1 diluted andneutralized) to the erlenmeyer flask. (The glycerol solution prepared by the lab personnel willbe ready to use.)Add 2 drops of phenolphthalein to the erlenmeyer flask and titrate with standardized NaOHsolution until the pink color is observed.Reaction equation:Calculations:Boric acid concentration of the original sample is calculated as g/L and w/v %.(MWH3 BO3 61.82 g/mol)First, the moles of NaOH consumed during titration can be calculated from the followingequation using the volume of NaOH that is consumed in the titration and the molarity of theNaOH.nNaOH MNaOH VNaOHAccording to reaction equation:If1 mol NaOH reacts with1 mol H3BO3nNaOHx mol H3BO3reacts withFrom this ratio, the moles of H3BO3 in the diluted sample (π₯ nH3 BO3 ) is calculated. Then themolarity of the diluted sample is calculated from x.10
MH3 BO3 π₯VH3 BO3The molarity of the original sample (Mπ πππππ ) then can be calculated by multiplying themolarity of the diluted sample by the dilution factor.Mπ πππππ MH3 BO3 DFThe molarity is multiplied by the molecular weight to convert the concentration of the originalsample to g/L:C(g L) Mπ πππππ 61.82Concentration of the original sample is calculated as w/v %.(w/v) % C(g/L) g100 mLg1000 mL(w/v) % C(g/L) 10In your report, explain how to prepare 100 mL of 2 % (w/v) boric acid solution by using theoriginal sample you have received with dilution calculations.11
PERCENT PURITY DETERMINATION OF ASPIRIN SAMPLESExperimental procedure:Carefully weigh 0.1-0.2 gram of solid aspirin sample into an erlenmeyer flask and note theexact amount. Dissolve it in 25 mL 60 % (v/v) ethanol. (Since the solubility of aspirin is verylow in water, ethanol solution is used.) Add 1-2 drops of phenolphthalein and titrate withstandardized NaOH until the pink color is observed.Reaction equation:Calculation:Percent amount of the pure aspirin will be calculated. (MWππ πππππ 180 g/mol)First, the moles of NaOH consumed during titration can be calculated from the followingequation using the volume of NaOH that is consumed in the titration and the molarity of theNaOH.nNaOH MNaOH VNaOHAccording to reaction equation:If1 mol NaOHnNaOHreacts with1 mol Aspirinx mol AspirinFrom this ratio, the moles of aspirin in the reaction (π₯ nππ πππππ ) is the moles of aspirin in theweighed amount. Using this mol (x), the mass of aspirin in the weighed sample can becalculated.mππ πππππ π₯ MWππ πππππThe amount of pure aspirin is calculated as the % of the sample weighed.% ππ’πππ‘π¦ mππ πππππ 100mπ€πππβππ12
CaCO3 PURITY DETERMINATIONCalcium carbonate (CaCO3) cannot be directly titrated since itβs not soluble in water. At thispoint, it can be analyzed using the back titration method.In back titration, a sample solution (A) reacts with excess amount of standard solution βBβ. Asa result of the reaction, a portion of the solution B remains in the erlenmeyer flask in excess. Atitration is then performed with a titrant (standard solution) βCβ to react with the remaining Bsolution. This whole process is called as βBack titrationβ.Experimental procedure:Carefully weigh 0.1-0.2 g of solid CaCO3 sample into an erlenmeyer flask and note the exactamount. Add 50 mL of standard HCl solution from a burette into the erlenmeyer flask. A portionof the added acid reacts with CaCO3. Heat the erlenmeyer on wire gauze for 2-3 minutes inorder to remove the CO2. Add 1-2 drops of phenolphthalein and titrate the remaining acid inthe erlenmeyer flask with standard NaOH until a permanent pink color is observed.Reaction equation:CaCO3 2HClCaCl2 H2O CO2HCl NaOHNaCl H2OCalculations:Percent amount of CaCO3 will be calculated.First, the moles of NaOH consumed during titration can be calculated from the followingequation using the volume of NaOH that is consumed in the titration and the molarity of theNaOH.nNaOH MNaOH VNaOH13
According to the reaction equation; HCl NaOHIf1 mol NaOH reacts withnNaOH mol NaOH reacts withNaCl H2O1 mol HClx mol HClIn this reaction, since the mol ratio of NaOH and HCl is 1:1, the moles of HCl (x), which reactswith NaOH, equals to the moles of consumed NaOH.Then the total moles of HCl, added into the erlenmeyer flask, is calculated as below:nHCl(total) MHCl VHClWhen we subtract the moles of HCl, which neutralized the NaOH, from the total moles of HCl,we find the moles of HCl, which reacted with CaCO3.moles of HCl, which reacts with CaCO3 nHCl(total) π₯According to the reaction equation; CaCO3 2HClIf2 moles HCl react withnHCl(total) π₯ mol HCl reacts withCaCl2 H2O CO21 mol CaCO3y mol CaCO3The moles of CaCO3 found from this ratio (y) is the moles of CaCO3 in the erlenmeyer flask,which means the moles of CaCO3 in the weighed solid. The mass of CaCO3 in the weighedsample can be calculated using y. (MWCaCO3 100 g/mol)mCaCO3 π¦ MWCaCO3The amount of pure CaCO3 is calculated as the % of the sample weighed.mCaCO3% ππ’πππ‘π¦ 100mπ€πππβππ14
H3PO4 (PHOSPHORIC ACID) DETERMINATIONPolyprotic acids contain more than one mol ionizable hydronium ions per mol of acids, forexample phosphoric acid (H3PO4), carbonic acid (H2CO3) sulfuric acid (H2SO4), oxalic acid(H2C2O4). They ionize to give more than one H ions per molecule. Phosphoric acid contains 3protons has three acidities different from each other.Polyprotic acids ionize to three steps. Each step gives one proton and for each step the effectvalue is 1. Thus, total effect value is three.It is difficult to titrate 3rd proton of phosphoric acid as it is very weak (Ka3 4.20x10-13).Experimental procedure:Dilute the given sample (20 mL) to 100 mL with distilled water. Transfer 25 mL of sample toan erlenmeyer flask.Add 2 drops of bromocresol green and phenolphthalein.Titrate with 0.1 M NaOH until blue-green color and note the volume of titrant used (V1).Continue titration until violet color and note the volume of titrant used for second part (V2).Reaction equation:H3PO4 NaOH NaH2PO4 H2O(End point of bromocresol green )Ka1 7.11x10-3NaH2PO4 NaOH Na2HPO4 H2O(End point of phenolphthalein)Ka2 6.34x10-8H3PO4 2NaOH Na2HPO4 2H2OTotal acidityCalculations:The concentration of phosphoric acid in the sample is calculated in g / L. ( MWH3PO4 98g/mol)Determination of 1st proton (1st acidity)First, the moles of NaOH consumed during titration can be calculated from the followingequation using the volume of NaOH that is consumed in the titration and the molarity of theNaOH.nNaOH MNaOH V115
According to reaction equation:If1 mol NaOH reacts withnNaOH mol NaOH reacts with1 mol H3PO4x mol H3PO4From this ratio, the moles of H3PO4 in the diluted sample (π₯ nH3 PO4 ) is calculated and themolarity of the diluted sample is calculated from x.MH3 PO4 Vπ₯H3PO4The molarity of the original sample (Mπ πππππ ) can then be calculated by multiplying themolarity of the diluted sample by the dilution factor.Mπ πππππ MH3 PO4 DFFinally, the molarity is multiplied by the molecular weight to convert the concentration of theoriginal sample to g/L:C(g L) Mπ πππππ 98Determination of 2nd proton (2nd acidity):First, the moles of NaOH consumed during titration can be calculated from the followingequation using the volume of NaOH that is consumed in the titration and the molarity of theNaOH.According to reaction equation:nNaOH MNaOH V2If1 mol NaOH reacts withnNaOH mol NaOH reacts with1 mol H3PO4x mol H3PO4From this ratio, the moles of H3PO4 in the diluted sample (π₯ nH3 PO4 ) is calculated and themolarity of the diluted sample is calculated from x.MH3 PO4 Vπ₯H3PO4The molarity of the original sample (Mπ πππππ ) can then be calculated by multiplying themolarity of the diluted sample by the dilution factor.Mπ πππππ MH3 PO4 DF16
Finally, the molarity is multiplied by the molecular weight to convert the concentration of theoriginal sample to g/L:C(g L) Mπ πππππ 98Determination of total acidity:Transfer 25 mL of sample to an erlenmeyer flask.Add 2 drops of phenolphthalein.Titrate with 0.1 M NaOH until pink color and note the volume of titrant.nNaOH MNaOH VNaOHAccording to reaction equation:If2 mol NaOH reacts with1 mol H3PO4nNaOH mol NaOH reacts withx mol H3PO4From this ratio, the moles of H3PO4 in the diluted sample (π₯ nH3 PO4 ) is calculated and themolarity of the diluted sample is calculated from x.MH3 PO4 Vπ₯H3PO4The molarity of the original sample (Mπ πππππ ) can then be calculated by multiplying themolarity of the diluted sample by the dilution factor.Mπ πππππ MH3 PO4 DFFinally, the molarity is multiplied by the molecular weight to convert the concentration of theoriginal sample to g/L:C(g L) Mπ πππππ 9817
REDOX TITRATIONSRedox titration is a titration based on the oxidation-reduction reaction between analyte andtitrant.PERMANGANOMETRYTitration in which potassium permanganate (KMnO4) is used as a standard solution is calledpermanganometry. The half reaction of permanganate (MnO 4 ) is different in acidic and basicmedium.Acidic medium: MnO 4 8H 5e Alkali medium: MnO 4 2H2 O 3e Mn 2 4H2 OMnO2 4OH In this laboratory, the permanganometric titrations will be performed in acidic medium.In permanganometric titrations indicator is not used. MnO 4 solution has a purple color whereas 2 2its reduction product Mn is colorless. When all the species that reduces MnO 4 to Mn areconsumed, the colorless solution in the erlenmeyer flask becomes pink-purple with the additionof 1 excess drop of KMnO4. The occurrence of pink-purple color indicates the end point of thetitration. That is why, KMnO4 is an βauto indicatorβ.Preparation of 0.02 M 1 L KMnO4 SolutionWeight around 3.2605-3.3605 g of KMnO4 into a beaker. This amount is 0.1-0.2 g more than0.02 mol KMnO4. (Molar mass of KMnO4: 158.032 g/mol)Add 400-500 mL distilled water to the beaker and dissolve the solid KMnO4 by mixing with aglass-rod. Transfer the solution to a 1 L volumetric flask. In order to dissolve the remainingsolid KMnO4, add 100-200 mL of distilled water to the beaker and mix it with the glass-rod.Transfer the solution into the same flask. Repeat this step until all the solid KMnO4 in the beakeris dissolved. (Be careful! Do not add more water than 1 L in total). Fill the flask up to the 1 Lmark with distilled water. Shake the volumetric flask to make sure all the KMnO4 is dissolvedin the flask. Put the solution into an amber-color bottle and keep it in dark for 1 week.After waiting 1 week, filter the solution by glass fibers into a clean amber glass bottle. The finalsolution is kept in dark.Standardization of KMnO4 SolutionExperimental procedure:Weight 0.1-0.2 g (take a note of exact amount) of oxalic acid (H2C2O4.H2O) and dissolve it inaround 100 mL of distilled water in an erlenmeyer flask. Add 10 mL of Β½ diluted H2SO4. (Theacid solution will be ready to use). Heat up the erlenmeyer flask on a bunsen burner for 3-4minutes (should not be boiled!) and then cool it down until it is cool enough to touch.Titrate the solution with KMnO4 solution until permanent pink color.18
After each student calculates the molarity of the KMnO4 solution, the results will be evaluatedwith the assistant and the average molarity will be reported for each lab bench.Reaction equation:2/ MnO 4 8H 5e Mn 2 4H2 OπΆ2 π4 2 5/2πΆπ2 2e 2 2MnO 4 16H 5πΆ2 π4 2Mn 2 8H2 O 10πΆπ2Calculations:First, the moles of oxalic acid consumed during titration can be calculated from the followingequation using the mass of oxalic acid that is weighed and the molecular weight of the oxalicacid. (MW: H2 C2 O4 . H2 O : 126.07 g/mol)nH2 C2 O4.H2O mH2 C2O4 .H2 OMWt H2 C2O4 .H2 OnH2 C2 O4 .H2 O nH2 C2O4According to reaction equation:If5 moles oxalic acid reacts with2 moles KMnO4nH2 C2O4 moles oxalic acid reacts withx moles KMnO4Then, the molarity of KMnO4 is calculated from the following equation using the volume ofKMnO4 that is consumed in the titration and the mol of the KMnO4 (π₯ nKMnO4 ), which wascalculated from the above ratio.MKMnO4 π₯VKMnO419
FeSO4 DETERMINATIONExperimental procedure:Fe2 is oxidized to Fe3 in acidic medium by MnO4- Dilute the 20 mL FeSO4 sample in thevolumetric flask to 100 mL with distilled water and mix it well. Transfer a portion of 25 mLdiluted sample to an erlenmeyer flask and add 10 mL Β½ diluted H2SO4. Add 50-100 mL distilledwater and titrate with standardized KMnO4 solution until pink color.Reaction equation:MnO4- 5Fe2 8H Mn2 5Fe3 4H2OCalculations:Calculate the concentration of the iron (II) sulfate of the sample in g/L(MWFeSO4 152 g/mol)Firstly, calculate the moles of reacted KMnO4 using the molarity of KMnO4 and the volume ofKMnO4 used in the titration:nKMnO4 MKMnO4 VKMnO4According to the reaction:If1 mol KMnO4 reacts with5 mol FeSO4nKMnO4 mol KMnO4 reacts withx mol FeSO4Calculate the moles of diluted FeSO4 (π₯ nFeSO4 ) is using above proportion. Using x, calculatethe molarity of diluted FeSO4:MFeSO4 π₯VFeSO4Calculate the molarity of sample by multiplying the molarity of diluted sample with dilutionfactor:Mπ πππππ MFeSO4 DFFinally, convert the molarity of sample to concentration in g/L:C(g L) Mπ πππππ 15220
IODIMETRY AND IODOMETRYTITRATION WITH IODINEIodine is a good oxidizing agent. Since Iodine/Iodide ((I2/I-) has a standard redox potentialbetween strong oxidizing agent and strong reducing agent, it has a wide range of applications.While strong oxidizing agent oxidize iodide (I-) to iodine (I2), strong reducing agents reduceiodine to iodide.Since solubility of iodine in water is very low, KI is added to dissolve it by formation of I3(triiodide) complex:I2 I- I3Since triiodide/iodide (I3-/I-) pair has same reduction potential with iodine/iodide (I2/I-) pair(0.54 V), I2 can be written instead of I3- for avoiding confusion.There are two type of iodine titrations; iodimetry (Direct method) and iodometry (Indirectmethod)Iodimetry (Direct method): In this method, a reducing agent is titrated with a standard iodinesolution. Reaction medium either neutral or mild acidic. The analytes having standard reductionpotentials lower than iodine/iodide pair are oxidized
and instrumental techniques will be used for quantitative analysis. Quantitative Analytical Methods Classical Methods Instrumental Methods If the analysis is carried out solely using solutions of chemical substances, this is called as classical analysis. - Gravimetric analysis - Volumetric analysis If the analysis is performed using a
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