TITRATION8. Potassium manganate(VIl) / oxalic acid 1. Determination of the percentage purity of sample of oxalic acid solution. ‘You are provided with two solutions as Follows: C10 isa solution containing 2.8 gms of potassium manganate (VII), KMNO, per litre, (C-L1 Is a solution prepared by dissolving 6.25 gms of impure sample of oxalic acid crystals (H2€204.2420) per litre. Procedure: Rinse and fill the burette with potassium manganate (VI) solution C-10 (kMn0,). Pipette out 20, ‘mL or 25 ml of the oxalic acid solution C-11 (HyC204.2H20) in a clean conical flask. To this, add 20 mL of dilute sulphuric acid (HyS0,) C-12, specially provided for this purpose. Warm the ‘contents of the fiask to 60°C -70°C. The heating should be continued tll the first bubble appears ‘at the bottom of the flask. Remove the conical flack fram fire and titrate this solution by running ‘solution C-10 from the buratte, shake the solution constantly tll a permanant pale pink colour is ‘obtained. Ensure that the pink colour obtained does not disappear on shaking the contents of the: conical flask. Repeat the above procedure to get at least two concordant readings. Tabulate your readings. State: (2) The capacity ofthe pipette used (0) The Ure value you Intend to use In your calculations. ‘The equations forthe above reactions areas fllows: 2k0INO, + 44,50, + SHsC,04 — K;SO, + 2MNSO, + BHO + 10CO, 2MnO4 + SCIO¥ + 16 HY 2MrA* + 10003 + BH;0State: (a) The capacity of the pipette used. (b) The titre value you intend to use in your calculations. The equations for the above reactions are as follows: 2KMNOg + 4HyS04 + 5H2C20, — KzS04 + 2MnSO, + 8H,0 + 1060, 2MNOg- + 5C,042 + 16 H* + 2Mn2* + 10CO2 + SHO [K=39, Mn=55, C=12, O=12, H=1] Calculate the following: 1. The molarity of potassium manganate (VII) solution C-10. 2. The molarity of oxalic acid solution C-11. 3. The strength of oxalic acid solution in gms per li 4. The percentage purity of the sample of oxalic acid solution. Answer:Answer: Observation Table ‘Obs | Initial Barete Reading | Final Burete reading _| Vol of KMnO, used T o 20.6 OR 25.8 20.5 OR 25.8 z 0 20.6 OR 25.9 20.5 OR I5.5 3 a 20.7 OR 25.8 20.7 ORI5.8 Let the titre value be 20.6 mL (with 20.0 mL pipette) OR Lethe tite value be 25.8 mL (with 25.0 ml pipete) @ Molarity of the solution C-10 (KMnO,) ="=SE=ES0S* = 22 (Gi) Molarity ofthe solution, C-11 (H:C:0,2#0) M Let the tive value be 19.1 mL Let the titre value be 23.9 mL Mz x200 10 ‘Myx280 8 ‘M:= 0.0456 M M:=0.0456 M (Gli) Suength of C-11 (Oxalic acid) in gms perlitre. Strength of C-11 = Molarity of C-11 x Mol.wt = 0.0456 x 126= 5.7456 gm Litre (Gv) Percentage purty of oxalic acid Serangth of pure samote i g/t es 100 of impure sample ing/E 7456 x100=91.93%2.Determination of water of crystallization of oxalic acid. ‘You are provided with two solutions as follows: ©-10 Is solution containing 2.8 gms of potassium manganate (vit), KMNO« per litre. CAL is a solution prepared by dissolving 5.83 oms of impure sample of oxalic acd crystals (HeC204.2420) per ire. Procedure: Rinse and fll the burette with potassium manganate (VIt) solution C-10 (KMIn0.). Pipette out 29 Im or 25 mi of the oxalic acid solution C-11 (HaCa0s.2#30) in a clean conical flask. To this, add 20 mL of dilute sulphuric acid (H»50,) C-12, specially provided for this purpose. Warm the ‘contents ofthe flask to 60°C 70°C, The heating should be continued till the first bubble appears _at the bottom af the flask, Remove the conical flask from fire and titrate this solution By running ‘Solution C-10 from the buratte, Shake the solution constantly tl a permanent pale pink colour is ‘obtained. Ensure that the pink colour abtained does not disappear on shaking the contents of the ‘conical flask. Repeat the above procedure to get atleast two concordant readings. Tabulate your readings. state: (a) The capacity of the pipette used. (b) The titre value you intend to use in your calculations. “The equations for the above reactions are as follows: 2KMNO: + 4H2505 + SH2Cz05 —> K2505 + 2MASO, + BHO + 10C02 2hno + SOs + 18H" — avin + 10CO: + BHO [k=39, nin=35, 2, 0=12, Hat]Calculate the following: i, The molarity of the solution of Potassium manganate (VII) C-10. ii, The molarity of hydrated ammonium oxalic acid solution C-11. {il The molecular mass of hydrated oxalic acld deduced from the experimental data. iy, The numerical value of x in HsCz0..xH30 Answer: tert Table ‘Oi [Tan Bute Reng | Fan Baie mading [Vola f NOL H ° SORISS 2s 0RIE = o TORY, DTORIST {Letthetine vahuebe 20 6m (vith 20 0mL pipette) OR Lotthotere valve be 25 Smt (th 25 Omak pete) @ Motasty ofthe eantion C10 (KAn0)) = SESESEEEEE, () Molany ofthe solution, C-11 (hydrated oxahc ac) oor Lette tere vaue be 19. mL Letthe ine valabe 239 mL Mo=0085500 Moose G@ Nelecdarmassofydtedorabcacd Mole Mase =Smsal=- a Gey Vatwofe “Moteuarinasofh rated cnaicaci= Molcdarmassotantydeusenaticail +18 212785 =904 Ite mr ton 02 ox Suengt of CII = Melonty Malt. 13553 =0.0456(90~ 18) 10232ORGANIC COMPOUNDSIdentification of organic compounds and functional groups based on observations 1. Alcoholic group- glycerol Experiment Observation a) To 3 mL of 1% borax solution taken in a clean test tube, few drops of phenolphthalein solution are added. To this solution, few Pink colour gets drops of sample is added and shaken. discharged, b) To i mL of the sample solution ,4-5 drops of phenol Is added followed by 2-3 drops of cone. sulphuric acid. The mixture is Ares coloured heated, Cooled. Diluted with water and finally ammonium produced hydroxide solution Is added. ¢) To 1 mL of the sample solution, 1 mL of copper sulphate solution Is added and then 1 mL of sodium hydroxide solution Is added. A blue coloured solution Is produced.2. Aldehyde group- formaldehyde Experiment Observation a) To 2 mL of the sample few crystals of resorcinol is added and shaken, Then 1 mL of conc. sulphuric acid Is along the side of the test tube, ‘A red ring is formed at the Junction of the two liquids while a white ppt forms in aqueous layer b) To 2 mL of the sample , 1 mL of freshly prepared pyrogallol solution is added, The content is shaken, 2 mL of conc. HC! is added and then the content is warmed in a water bath. ‘A white ppt is formed which readily turns pink and then deep red. c) To 2 mL of the sample, 1 ml of tollen’s reagent is added and warmed in hot water bath. A shiny silver mirror Is formed.4.Carboxylic acid- benzoic acid Experiment Observation a) The sample solution is treated with moist blue litmus solution, The solution turns red. b) To 2 mL of the sample solution, 2 mL of sodium bicarbonate solution is added. Effervescence seen, ¢) To 2 mL of the sample solution, 2 mL of ethanol Is added and few drops of cone. H,SO, are added, The mixture Is warmed. A pleasant fruity smell is obtained,5. Amino group-aniline Experiment Observation a) To 1 mL of the sample solution, 1 mL of cone. HCI Is added. Now, few drops of neutral ferric chloride solution Is added and then diluted with water. Pale green colouration. b) To 4 mL of the sample solution 2-3 drops of sodium hypochlorite solution is added and shaken. Violet or purple colouration is obtained, ¢) To 1 mL of the sample solution few drops of dilute sulphuric acid is added followed by 1 mL of potassium dichromate solution, The mixture is shaken and warmed, A deep red colouration Is produced which finally changes to deep blue or black.Characteristic Tests of carbohydrates and proteins 1. Carbohydrate-glucose Experiment Observation a) To 2 mL of the sample solution, 1 mL of Fehling’s solution is added and warmed, A brick red ppt Is obtained, b) To 2 ml of the sample solution, 2-3 drops of a- naphthol solution is added. After that, conc. sulphuric acid is slowly added along the side of the test tube. A violet ring is formed at the junction of the two liquids, ¢) To 1 mL of the sample solution, imL of lead acetate solution is added followed by ammonium hydroxide solution. The content Is boiled. A white ppt is formed which turns to salmon pink on boiling with ammonium hydroxide.