EDTA forms a colourless complex with free metal ions. Metal ion (Ca 2+ or Mg 2+ ) + EDTA

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1 Expt. No. : 01 Date : ESTIMATION OF HARDNESS OF WATER BY EDTA METHOD AIM: To determine the hardness of given water sample by EDTA method. APPARATUS: Burette, Pipette, Conical Flask, Beakers, Wash Bottle and Burette Stand. CHEMICALS: EDTA solution, Standard Hard Water, Eriochrome Black-T, Ammonical Buffer Solution. PRINCIPLE : Hard water contains calcium and magnesium ions which form wine red colour complex with the indicator, Eriochrome Black-T. Ca 2+ + Eriochrome black T Indicator EDTA forms a colourless complex with free metal ions. [Ca Indicator Complex] Wine Red Colour Metal ion (Ca 2+ or Mg 2+ ) + EDTA Metal ion - EDTA Complex Stable complex When free metal ions are not available EDTA extracts the metal ions from the metal ion indicator complex there by releasing the free indicator, EDTA + [Metal ion indicator complex] [Metal ion EDTA] + Indicator Wine Red Colour Blue Colour The reactions take place at a ph = 10 in order to maintain it use a buffer made of ammonium chloride and ammonium solution. PROCEDURE: Part A : - Standardization of EDTA Solution i. Rinse and fill the burette with EDTA solution. ii. Pipette out ml of Standard hard water solution into a clean conical flask. iii. Add 5ml of ammonical buffer solution and 2-3 drop of EBT indicator, the solution becomes wine red. iv. Titrate against EDTA till wine red colour changes to blue. v. Note the volume of EDTA used (V 1 ml). vi. Repeat the titrations till the concordant reading are obtained. Part B : - Estimation of Total Hardness i. Pipette out ml of water sample into a clean conical flask. ii. Add 5ml of ammonical buffer solution and 2-3 drop of EBT indicator, the solution becomes wine red. iii. Titrate against EDTA till wine red colour changes to blue. iv. Note the volume of EDTA used (V 2 ml). v. Repeat the titrations till the concordant reading are obtained. Part C : - Estimation of Permanent Hardness i. Pipette out 100ml of hard water sample into a beaker and boil the water till the volume reduces to 50ml. ii. Cool the solution and filter. iii. Make up the solution up to the mark of 100ml. iv. Pipette out ml of Standard boiled hard water into a clean conical flask. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 1

2 v. Add 5ml of ammonical buffer solution and 2-3 drop of EBT indicator, the solution becomes wine red. vi. Titrate against EDTA till wine red colour changes to blue. vii. Note the volume of EDTA used (V 3 ml). viii. Repeat the titrations till the concordant reading are obtained. RESULT: i. Molarity of EDTA solution is M. ii. Molarity of standard hard water M. iii. The amount of total hardness in terms of CaCO 3 equivalent weight is ppm. iv. The amount of permanent hardness in terms of CaCO 3 equivalent weight is ppm. v. The amount of temporary hardness in terms of CaCO 3 equivalent weight is ppm. OBSERVATION AND CALCULATIONS: Part A : - Standardization of EDTA Solution S.No. Volume of Standard Hard Water Burette Readings Initial (ml) Final (ml) Volume of EDTA used V 1 ml M 1 V 1 = M 2 V 2 M 1 = Molarity of Standard Hard Water V 1 =Volume of Standard Hard Water M 2 =Molarity of EDTA V 2 = Volume of EDTA = M = ml =? M = ml M 2 = Part B : - Estimation of Total Hardness M 1V V Burette Readings S.No. Volume of Water Sample Initial (ml) Final (ml) 2 1 Volume of EDTA used V 2 ml M 2 V 2 = M 3 V 3 M 2 = Molarity of EDTA = M V 2 = Volume of EDTA = ml M 3 = Molarity of Standard Hard Water =? M V 3 = Volume of Standard Hard Water = ml M 3 M 2V2 = V3 = M Prepared by T K MOHAN (mohanchemist@gmail.com) Page 2

3 Formula: Titre Value X Concentration of EDTA X 50 X 1000 Total Hardness = Volume of the sample = ppm Part C : - Estimation of Permanent Hardness Burette Readings S.No. Volume of Hard Water Sample Initial (ml) Final (ml) Volume of EDTA used V 3 ml Formula: Permanent Hardness = Total Hardness Temporary Hardness Titre Value X Concentration of EDTA X 50 X 1000 Volume of the sample = Temporary Hardness + Permanent Hardness = Total Hardness Permanent Hardness = ppm. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 3

4 Expt. No. : 02 Date : DETERMINATION OF COPPER BY EDTA METHOD AIM: To estimate the amount of copper present in the given solution by complexometric method. APPARATUS: Burette, Pipette, Beaker, Conical Flask, Burette Stand. CHEMICALS: MgSO 4, EDTA, fast sulphone black F, ammonical buffer, Eriochrome black-t PRINCIPLE: Copper forms complexes with EDTA in ammonia solution, which is colourless and stable. Fast sulphone black F is the indicator which is bright green in its colour forms complex with copper ions to produce an unstable complex which is pale blue in its colour. The copper solution is first treated with buffer and indicator to produce unstable pale blue complex which is titrated against EDTA solution until the colour change from pale blue to dark green takes place. Repeat the titration to get concordant values. Cu In [Cu In] Bright green pale blue [Cu In] + EDTA [Cu EDTA] + In Pale blue colourless Bright green PROCEDURE: Part A: Standardisation of EDTA Solution: Rinse the burette with EDTA solution and take EDTA solution upto the mark. Pipette out ml of MgSO 4 solution into a conical flask, add 5ml of buffer solution and 2-3 drops of EBT indicator. Titrate the wine red coloured complex with EDTA till a blue colour end point is obtained. Repeat the titration to get concordant values. Let the titre value be x ml. Part B: Estimation of Copper Solution: Make up the given solution upto the mark with distilled water and shake the flask well for uniform concentration. Pipette out ml of copper solution into clean 250ml conical flask, add ml of distilled water, 5ml of ammonia and 5 drops of the fast sulphone black F indicator. Titrate the resulting pale blue coloured complex with EDTA till dark green colour endpoint is obtained. Repeat the titration to get concordant values. Let the titre value be y ml. RESULT: i. Amount of copper present in the given solution is g. OBSERVATION AND CALCULATIONS: Molarity of MgSO 4 (M 1 ) = M Part A: Standardisation of EDTA Solution: S.No. Volume Of MgSO 4 V 1 ml Initial Burette readings Final Volume Of EDTA V 2 ml Prepared by T K MOHAN (mohanchemist@gmail.com) Page 4

5 Molarity of EDTA (M 2 ): Part B: V 1 M 1 V 2 M 2 = n 1 n 2 n 1 =n 2 = 1 V 1 = Volume of MgSO 4 = ml M 1 = Molarity of MgSO 4 = M V 2 = Volume of EDTA solution = ml x M 1 M 2 = = M Titre value (V 2 ) Estimation of Copper Solution: S.No. Volume Of Copper V 3 ml Initial Burette readings Final Volume Of EDTA V 2 ml Molarity of Copper Solution: V 2 M 2 V 3 M 3 = n 2 n 3 V 2 = Volume of EDTA = ml M 2 = Molarity of EDTA = M V 3 = Volume of Copper solution = ml V 2 M 2 n 3 M 3 = x V 3 n 2 n 2 =n 3 = 1 Titre value x M 2 M 3 = = M Amount of copper present in the given solution M 3 Molecular weight of copper volume of solution g 1000 = g Prepared by T K MOHAN (mohanchemist@gmail.com) Page 5

6 Expt. No. : 03 Date : ESTIMATION OF DISSOLVED OXYGEN IN WATER SAMPLE AIM: To estimate the amount of dissolved oxygen (DO) in the given water sample. APPARATUS: Burette, Pipette, Conical Flask, Beakers, Wash bottle, Burette stand, BOD bottle. CHEMICALS: 48% Manganese sulphate solution, Alkali-Iodide-Azide solution, Conc.Sulphuric acid, Starch indicator, 0.025N sodium thio sulphate solution, 40% KCl solution, Sample water, Distilled water. PRINCIPLE: Dissolved Oxygen can be determined by iodometric titration. Dissolved Oxygen present in water oxidises by KI liberating an equivalent amount of iodine by which it is titrated against a standard solution using starch as an indicator. An oxygen carrier like manganese hydroxide must be used to bring about the reaction between KI and dissolved oxygen because of molecular oxygen in water is not capable of reacting with KI. Manganese is produced by the action of potassium hydroxide or sodium hydroxide and manganese sulphate. 2KOH + MnSO 4 Mn(OH) 2 + K 2 SO 4 2Mn(OH) 2 + O 2 2MnO(OH) 2 Basic Manganic oxide Oxygen carrier 2MnO(OH) 2 + H 2 SO 4 MnSO 4 + 2H 2 O + (O) 2KI + H 2 SO 4 + (O) K 2 SO 4 + H 2 O + I 2 2Na 2 S 2 O 3 + I 2 2NaI + Na 2 S 4 O 6 Sodium Tetrathionate The nitrates present in the water interfere with the dissolved oxygen of water, since these ions liberate iodine from KI. Sodium azide is added to water which reacts with nitrate to decompose it as follows: 2NaN 3 +H 2 SO 4 2N 3 H + Na 2 SO 4 HNO 2 + N 3 H N 2 O + N 2 + H 2 O FORMULA :- The amount of dissolved oxygen in the given water sample Titre value Conc. of hypo mg / lit Voluime of water sample Where 8 is the equivalent weight of oxygen. PROCEDURE :- 1. Collect water sample in a 300ml capacity of BOD bottle and add 1ml of KCl solution. 2. Add 2ml of manganese sulphate and 2ml of Alkali-Iodide-Azide solution. 3. Stopper the BOD bottle immediately. 4. Appearance of brown precipitate indicates the presence of DO. 5. Mix well by inverting the bottle 2 to 3 times and allow the brown precipitate to settle down. 6. Add 2ml of Conc. of H 2 SO 4 solution to dissolve the precipitate. 7. Take ml of this solution in to a clean conical flask. 8. Titrate the liberated Iodine with standard Hypo solution present in the burette. 9. Add 2ml of starch solution when the colour of solution becomes pale yellow, the solution turns to blue colour. 10. Continue the titration till the blue colour is disappeared. 11. Note the volume of hypo used (V ml) Prepared by T K MOHAN (mohanchemist@gmail.com) Page 6

7 12. Repeat the titration till concordant readings are obtained. 13. Calculate the amount of dissolved oxygen in the given water sample by using the formula. RESULT : -The amount of dissolved oxygen in the given water sample = mg/lit. OBSERVATION and CALCULATIONS: - Burette = Standard Hypo solution (0.025N). Conical flask = ml water sample consists of liberated Iodine. Indicator = 2ml Starch Solution. End Point = Blue to colour less S.No. Volume of Sample (ml) Burette Readings Initial Final Volume of Hypo used (Vml) V Conc. of hypo 8100 Dissolved oxygen in the given water sample mg / lit = mg/lit Prepared by T K MOHAN (mohanchemist@gmail.com) Page 7

8 Expt. No. : 04 Date : ESTIMATION OF COPPER BY IODOMETRY AIM: To estimate the amount of Copper present in the whole of given solution by using approximately N/ solution of Sodium thiosulphate and few crystals of Potassium dichromate. APPARATUS: Burette, Pipette, Conical Flask, Burette Stand, Standard Flask, Weighing bottle. CHEMICALS: Copper solution, Ammonia, CH 3 COOH, Starch indicator, KI, HCl, K 2 Cr 2 O 7. PRINCIPLE : K 2 Cr 2 O 7 is an oxidising agent. It liberates nascent oxygen atoms in the presence of dil.hcl. K2Cr2O 7 8HCl 2KCl 2CrCl 3 4H2O 3( O) This nascent oxygen oxidizes KI to I 2 in cold and in the presence of water. [2KI H O[ O] 2KOH ] 3 2 I2 3 6 [ Na2S2O3 I2 Na2S4O 2NaI ] K 2 Cr 2 O 7 3[O] 6 Na 2S4O6 Any Cupric salt in neutral medium when treated with potassium iodide form a white precipitate of Cuprous iodide and iodine is set free quantitatively. The liberated iodine is titrated against Sodium thiosulphate using starch as an indicator. 2CuSO 4 2KI 2CuI 2 K2SO4 5H2O 2CuI 2 Cu 2 I 2 I 2 2Na2S2O3 I2 Na2S4O6 2NaI Sodium tetrathionate From the above equation it is clear that 2Cu 2+ = I 2 = 2S 2 O 3 2- = 2e - The equivalent weight of Copper = 63.5 PROCEDURE: A) STANDARDISATION OF HYPO: Burette is cleaned, rinsed and filled with Sodium thiosulphate. Initial reading of the burette is noted. Pipette is cleaned and it is filled with K 2 Cr 2 O 7 solution. ml of K 2 Cr 2 O 7 solution is pipette out into clean conical flask and add 5 ml of conc.hcl, 1 g of NaHSO 3 and ml (or) 10 ml of 10% KI solution. The liberated iodine is titrated by adding of hypo from burette until straw yellow colour is obtained. Then 2 drops of freshly prepared starch indicator is added. The colour changes to blue; the titration is continued until blue colour changes to light green. Repeat the titration to get concurrent values. The normality of hypo is calculated. B) ESTIMATION OF COPPER SOLUTION: The given solution of copper is made up to the mark with distilled water and shaken well for uniform concentration. The burette is filled with hypo and initial reading is noted. Pipette is cleaned and filled with copper solution and it is pipette out into a clean conical flask and add few drops of ammonia to neutralize the mineral acid present in the copper solution. The precipitate is dissolved by adding drop by drop of acetic acid to get clear solution. To the above solution ml (or) 10 ml of 10% of KI is added. It is titrated by adding hypo from the burette till straw yellow colour is obtained. Then 2 drops of freshly prepared starch solution is added and titration is continued until white precipitate is obtained. The final reading is noted, difference between the final and initial volume gives the volume of the hypo required Prepared by T K MOHAN (mohanchemist@gmail.com) Page 8

9 to estimate ml of copper solution. Then calculate the normality and amount of copper is present in the given solution. RESULT : - Amount of copper present in the given solution= g OBSERVATION AND CALCULATIONS: Normality of K 2 Cr 2 O 7 N 1 = N STANDARDISATION OF HYPO: S.No. Volume of K 2 Cr 2 O 7 (V 1 ml) Initial Burette Readings Final Volume of Hypo (V 2 ml) Volume of potassium dichromate V 1 = ml Normality of K 2 Cr 2 O 7 N 1 = N Volume of Hypo V 2 = ml Normality of Hypo N 2 =? N N2 N1V 1 V2 = N ESTIMATION OF COPPER SOLUTION: S.No. Volume of Copper (V 3 ml) Initial Burette Readings Final Volume of Hypo (V 2 ml) Volume of Hypo V 2 = ml Normality of Hypo N 2 = N Volume of Copper solution V 3 = ml Normality of Copper solution N 3 =? N N3 N2V2 V3 = N N3 Eq. Wt. of copper Volume of solution Amount of copper present in the given solution g 1000 = g Prepared by T K MOHAN (mohanchemist@gmail.com) Page 9

10 Expt. No. : 05 Date : ESTIMATION OF IRON (II) USING DIPHENYLAMINE INDICATOR (DICHROMETRY INTERNAL INDICATOR METHOD) AIM: To estimate the amount of ferrous ion present in the whole of the given solution using a standard solution of potassium dichromate. APPARATUS: Burette, Pipette, Beaker, Conical Flask, Burette Stand, Standard Flask, etc. CHEMICALS REQUIRED: k 2 Cr 2 O 7, H 2 SO 4, Phosphoric acid, Iron Solution, Internal Indicator (Diphenylamine). PRINCIPLE: K 2 Cr 2 O 7 is an oxidizing agent; it liberates nascent oxygen atoms in the presence of dil.h 2 SO 4. K 2 Cr 2 O 7 +4H 2 SO 4 K 2 SO 4 + Cr 2 (SO 4 ) 3 + 4H 2 O + 3(O) The nascent oxygen oxidizes ferrous salt to ferric salt in cold in presence of an acid. 3[2FeSO 4 + H 2 SO 4 + (O) Fe 2 (SO 4 ) 3 + H 2 O] K 2 Cr 2 O 7 + 6FeSO 4 + 7H 2 SO 4 K 2 SO 4 + 3Fe 2 (SO 4 ) 3 + Cr 2 (SO 4 ) 3 + 7H 2 O 1 K 2 Cr 2 O 7 = 3(O) = 6Fe 2+. Equivalent weight of iron is and K 2 Cr 2 O 7 is 49 i.e.1/6 of its molecular weight. Indicator diphenyl amine employes appearance of blue violet colour in end point of titration. PROCEDURE: Estimation of Ferrous Ion:- The given solution of ferrous ion is made upto the mark with distilled water and shaken well for uniform concentration. Then burette is filled with K 2 Cr 2 O 7 solution, then pipette out ml of ion solution into a clean conical flask. Add 5ml of acid mixture (dil. H 2 SO 4 + H 3 PO 4 ) and few drops of diphenyl amine indicator. It is titrated against K 2 Cr 2 O 7 which is taken in the burette until violet blue colour is observed. Final reading is noted and experiment is repeated to get concordant value. RESULT: Amount of ferrous ion present in the given solution = g Prepared by T K MOHAN (mohanchemist@gmail.com) Page 10

11 OBSERVATION AND CALCULATIONS: Normality of K 2 Cr 2 O 7, N 1 = N Estimation of Ferrous Ion Vs K 2 Cr 2 O 7 :- S.No. Volume of ferrous solution (V 2 ml) Burette Readings Volume of K 2 Cr 2 O 7 Initial Final (V 1 ml) Volume of Potassium dichromate solution V 1 = ml Normality of Potassium dichromate solution N 1 = N Volume of ferrous ion V 2 = ml Normality of ferrous ion N 2 =? N V1 N1 N 2 V = N Amount of ferrous ion present in the given solution 2 Normality of ferrous ion (N2) Eq. wt. of Fe volume of solution g 1000 = g 2 Prepared by T K MOHAN (mohanchemist@gmail.com) Page 11

12 Expt. No. : 06 Date : DETERMINATION OF ALKALINITY OF WATER SAMPLE AIM: To determine the alkalinity of the given water sample. APPARATUS: Burette, Pipette, Conical flask, Beakers, Glazed tile, Wash bottle, Burette stand. CHEMICALS: Standard sulphuric acid (0.02 N), Phenolphthalein indicator, Methyl orange indicator, Water sample, Distilled water. PRINCIPLE: The alkalinity of a solution is a measure of its capacity to neutralize bases. 2 Alkalinity is due to OH, CO, HCO 3 3 ions. It is determined by titration against standard sulphuric acid using phenolphthalein and methyl orange indicators. Titration to ph 8.3 with phenolphthalein or the disappearance of pink will indicate phenolphthalein alkalinity. OH H H O 2 2 CO3 H HCO 3 Titration to ph 4.5 with methyl orange or the appearance of pink colour will indicate total alkalinity. (i.e., complete neutralization of OH -, CO 2-3 and HCO - 3 ions). HCO H H 2CO3 H 2O CO2 3 FORMULA: The amount of alkalinity interms of CaCO 3 equivalents Titre value Conc. of H 2SO ppm Volume of sample PROCEDURE: Part A: Phenolphthalein Alkalinity: 1. Rinse and fill the burette with 0.02N H 2 SO 4 solution. 2. Pipette out ml of water sample into a clean conical flask. 3. Add a drop of phenolphthalein indicator to the sample. 4. If pink colour develops titrate against 0.02N H 2 SO 4 till the pink colour disappears indicating ph Note the volume of H 2 SO 4 used (V 1 ml). 6. Repeat the titration to obtain concordant readings. 7. Calculate phenolphthalein alkalinity by using given below. V Phenolphthalein alkalinity ppm Part B: Total Alkalinity: 1. Rinse and fill the burette with 0.02 N H 2 SO 4 solution. 2. Pipette out ml of water sample into a clean conical flask. 3. Add 2 to 3 drops of methyl orange indicator to the sample. 4. If yellow colour develops, titrate against 0.02 N H 2 SO 4 solution till the pink colour appears indicating ph of Note the volume of H 2 SO 4 consumed (V 2 ml). 6. Repeat the titration to obtain concordant readings. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 12

13 7. Calculate total alkalinity by using the formula given below. V Total alkalinity = ppm RESULT: Phenolphthalein alkalinity of water sample in terms of CaCO 3 equivalents = ppm. Total alkalinity of water sample in terms of CaCO 3 equivalents = ppm. OBSERVATIONS and CALCULATIONS: Part A: Phenolphthalein Alkalinity: Burette = 0.02 N H 2 SO 4 solution Conical flask = ml of sample Indicator = Drop of Phenolphthalein End point = Pink to colourless. S.No Volume of Sample (ml ) Phenolphthalein alkalinity in terms of CaCO 3 equivalents Burette Reading (ml) Volume of H 2 SO 4 (V 1 ml ) Initial Final V ppm = ppm(or) mg/litre. Phenolphthalein alkalinity = ppm. Part B: Total alkalinity: Burette = 0.02 N H 2 SO 4 solution Conical flask = ml of sample Indicator = 2 to 3 drops of methyl orange End point = Yellow to pink S.No Volume of Water Sample (ml ) Total alkalinity in terms of CaCO 3 equivalents Burette Reading (ml) Volume of H 2 SO 4 (V 2 ml ) Initial Final V ppm = ppm (or) mg/litre. Total alkalinity ppm. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 13

14 Expt. No. : 07 Date : DETERMINATION OF ACIDITY OF WATER SAMPLE AIM: To determine the acidity of the given water sample. APPARATUS: Burette, Pipette, Conical flask, Beakers, Glazed tile, Wash bottle, Burette stand. CHEMICALS: Standard sodium hydroxide (0.02 N), Phenolphthalein indicator, Methyl orange indicator, Sodium thiosulphate (0.1 N), Water sample. PRINCIPLE: The acidity of a solution is a measure of its capacity to neutralize bases. Acidity is due to the presence of mineral acids like H 2 SO 4, HCl, HNO 3 and dissolved CO 2 in the form of H 2 CO 3. These acids can be estimated by titration against standard sodium hydroxide using methyl orange and phenolphthalein. Titration to ph 4.5 or a sharp change from faint orange to yellow of methyl orange indicator will indicate the neutralization of mineral acids. H + + OH - H 2 O Titration to ph 8.5 or the appearance of faint pink colour, by the use of phenolphthalein will indicate total acidity. (Complete neutralization of mineral acids and dissolved CO 2 ). Interference due to to presence of residual Chlorine can be removed by the addition of one drop of Sodium thiosulphate (Hypo) solution to the water sample. The acidity is measured interms of CaCO 3 equivalents and expressed in ppm or mg/litre. FORMULA: Acidity of water sample interms of CaCO 3 equivalents Titre value Conc. of NaOH ppm Volume of sample Where 50 is the equivalent weight of CaCO 3. PROCEDURE: Part A: Methyl Orange Acididty: 1. Rinse and fill the burette with 0.02 N NaOH solution. 2. Pipette out ml of water sample into a clean conical flask. 3. Add a drop of hypo solution and 2 drops of methyl orange indicator. The solution colour changes to orange. 4. Titrate the solution against 0.02 N NaOH solution till the colour changes from faint orange to yellow indicating ph of Note the volume of NaOH consumed (V 1 ml). 6. Repeat the titration to obtain concordant readings. 7. Calculate methyl orange acidity by using the formula given below. V Methyl orange acidity ppm Part B: Phenolphthalein Acidity (Total Acidity): 1. Rinse and fill the burette with 0.02 N NaOH solution. 2. Pipette out ml of water sample into a clean conical flask. 3. Add a drop of hypo solution and 2 drops of phenolphthalein indicator. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 14

15 4. Titrate the solution against 0.02 N NaOH solution till the appearance of faint pink colour indicating ph of Note the volume of NaOH consumed (V 2 ml). 6. Repeat the titration to obtain concordant readings. 7. Calculate total acidity by using the formula given below. V Total acidity ppm RESULT: Methyl orange acidity or Mineral acidity Phenolphthalein acidity or Total acidity Carbonic acid acidity of water sample = ppm. = ppm. = ppm. OBSERVATIONS and CALCULATIONS: Part A: Methyl orange acidity (Mineral acidity) Burette = 0.02 N NaOH solution Conical flask = ml water sample + Drop of Na 2 S 2 O 3 Indicator = Methyl orange; End point = Faint orange to yellow. S.No Volume of Water Sample (ml ) Burette Reading (ml) Volume of NaOH (V 1 ml ) Initial Final Methyl orange acidity = Titre value x conc. of NaOH x 50 x 1000 ppm Volume of sample V Methyl orange acidity ppm = ppm (or) mg/litre. Part B: Phenolphthalein acidity (Total acidity) Burette = 0.02 N NaOH solution Conical flask = ml water sample + Drop of Na 2 S 2 O 3 Indicator = Phenolphthalein; End point = Colourless to pink S.No Volume of Water Sample (ml ) Burette Reading (ml) Volume of NaOH (V 2 ml ) Initial Final Total acidity = Titre value x conc. of NaOH x 50 x 1000 ppm Volume of sample V Phenolphthalein acidity ppm = ppm (or) mg/litre. Acidity due to carbonic acid = Total acidity mineral acidity= ppm (or) mg/litre. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 15

16 Expt. No. :08 Date : ESTIMATION OF CHLORIDE CONTENT PRESENT IN WATER SAMPLE AIM: To estimate the amount of chloride present in the given water sample. APPARATUS: Burette, Pipette, Conical flask, Beakers, Glazed tile, Wash bottle, Burette stand. CHEMICALS: Standard Silver nitrate solution ( N), Potassium chromate indicator, Water Sample, Distilled water. PRINCIPLE: Chloride ions are present in water in the form of compounds like NaCl, CaCl 2, MgCl 2, etc. These chlorides are estimated by titrating with standard silver nitrate solution using potassium chromate indicator in the ph range of 7 to 8. This can be maintained by adding 1 N NaOH if the ph of the sample is less than 7 or by adding 1 N H 2 SO 4 if it is greater than 10. Silver chloride is precipitated quantitatively before red silver chromate is formed. Cl AgNO 3 AgCl NO3 ( White ppt) K2CrO4 2 AgNO 3 Ag 2CrO4 2KNO3 ( Black red ppt) FORMULA: Titre value Conc. of AgNO Chloride content in water sample mg / lit Voluime of water sample Where 35.5 is the equivalent weight of chlorine. PROCEDURE: Part A Titration of Water Sample with Standard AgNO 3 Solution: 1. Rinse and fill the burette with N AgNO 3 solution. 2. Pipette out ml water sample into a clean conical flask. 3. Add 2 or 3 drops of potassium chromate indicator. The solution turns yellow colour. Adjust to ph 7.0 to Titrate with N AgNO 3 solution until a faint distinct reddish brown colour is formed after brisk shaking. 5. Note the volume of AgNO 3 used (V 1 ml). 6. Repeat the titration till the concordant readings are obtained. Part B Titration of Distilled Water with Standard AgNO 3 solution: 1. Rinse and fill the burette with N AgNO 3 solution. 2. Pipette out ml distilled water into a clean conical flask. 3. Add 2 or 3 drops of potassium chromate indicator. The solution turns yellow colour. 4. Titrate with N AgNO 3 solution until a faint distinct reddish brown colour is formed. 5. Note the volume of AgNO 3 used (V 2 ml). 6. Repeat the titration till the concordant readings are obtained. Chloride content in the water sample ( V1 V2 ) mg / lit RESULT: The amount of chloride present in the water sample = mg/litre. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 16

17 OBSERVATIONS and CALCULATIONS: Part A Titration of Water Sample with Standard AgNO 3 Solution: Burette = N AgNO 3 solution Conical flask = ml water sample Indicator = 2 or 3 drops of K 2 CrO 4 End point = Yellow to Brick red S.No. Volume of Water Sample (ml) Burette readings (ml) Volume of AgNO 3 Used Initial Final (V 1 ml) Part B Titration of Distilled Water with Standard AgNO 3 solution: Burette = N AgNO 3 solution Conical flask = ml Distilled water Indicator = 2 or 3 drops of K 2 CrO 4 End point = Yellow to Brick red S.No. Volume of Distilled Water (ml) Burette readings (ml) Volume of AgNO 3 Used Initial Final (V 2 ml) Chloride content in the water sample ( V1 V2 ) mg / lit = mg/litre Chloride content in the water sample = mg/litre. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 17

18 Expt. No. : 09 Date : CONDUCTOMETRIC TITRATION OF STRONG ACID AGAINST STRONG BASE AIM: To estimate the strength of strong acid against strong base by conductometrically. APPARATUS: Conductivity Meter, Conductivity Cell, Micro Burette, Beaker, Glass rod CHEMICALS: HCl, NaOH PRINCIPLE: Conductometric titration is the volumetric analysis based upon the measurement of conductance during the course of titration. The number of free ions, charge on the free ions and mobility of the ions affect the conductance of an aqueous solution. When one electrolyte is added to another electrolyte, the change in number of free ions causes a change in the conductance. When a strong acid (HCl) is titrated against a strong base (NaOH), before NaOH solution is added from the burette, the acid solution has high conductivity due to highly mobile H + ions. When NaOH is added to the acid, the conductivity of the acid solution decreases due to neutralization of highly mobile H ions of the acid with OH ions of the base. H Cl NaOH Na Cl H2O Thus the conductance of the solution continues to decrease until the equivalent point is reached. Further, the addition of NaOH solution will increase the conductance by highly mobile hydroxyl ions. The point of intersection of the graph plotted by conductance of the solution against volume of alkali added correspond the endpoint of the titration. PROCEDURE: CONDUCTOMETRIC TITRATION: Fill the burette with standard 1N NaOH solution. Take ml of the given HCl solution in a 100ml beaker and dip the conductivity cell in it and measure the conductance initially. Now add NaOH from burette drop wise i.e.; 0.5ml for each addition. After each addition, stir the solution gently by shaking and note down the change in conductance. The measured conductance are recorded and tabulated in the table. Plot the graph between corrected conductance against volume of base added, the intersection of two straight lines gives the end point. Calculate the strength of the given strong acid (HCl) from the known strength of the NaOH solution. The corrected conductance is calculated by applying volume correction which is given by U V C C V Where C = Corrected Conductance C = Measured Conductance V = Volume of Acid U = Volume of Base PRECAUTIONS: 1. The conductivity cell should be never kept dry. 2. The electrode must be washed. RESULT: The strength of given hydrochloric acid solution is N. Prepared by T K MOHAN (mohanchemist@gmail.com) Page 18

19 OBSERVATIONS AND CALCULATIONS: S.No VOLUME OF BASE ADDED (ml) MEASURED CONDUCTANCE (Siemens) CORRECTED CONDUCTANCE U V C C V The titre value corresponding to the point of inflection in the end point graph is ml. Therefore, End Point titrevalue Normalityof NaOH(A) Strength of HCl Volume of HCl takenin bea ker Rough Graph: End Point volume(ml). (A) = = N. 25ml. Conductance Volume of Base (ml) End Point Prepared by T K MOHAN (mohanchemist@gmail.com) Page 19

20 Expt. No. : 10 Date : DETERMINATION OF VISCOSITY OF AN OIL BY RED WOOD VISCOMETER -I AIM: To determine the viscosity of lubricating oil by Red wood viscometer. APPARATUS: Red wood viscometer, Thermometer, Stop watch, Kohlraush flask. MATERIALS: Given lubricating oil. DESCRIPTION: Red wood viscometer-i is commonly used for determining the viscosity of thin lubricating oils of viscosity below 00sec. Red wood viscometer-i consists of an oil cup which is silver plated brass cylinder. The upper end of the cup is opened. The bottom of cylinder is fitted with jet with bore of diameter 1.62mm and length 10mm. The jet is opened or closed by a valve rod. The level to which cylinder is filled with oil is indicated by a pointer. The lid of the cup is fitted with a thermometer, which indicates the temperature of oil cup. Oil cup is surrounded by a cylindrical copper heating bath containing water. It is provided with the burner. Thermometer indicates the temperature of water. Outside the oil cup stirrer is placed carrying four blades for stirring the water in the bath for maintaining uniform desired temperature. The entire apparatus rests on three legs, provided at the bottom of the leveling screws. Koulrausch flask is used for receiving the oil from jet which is specially shaped glass flask. Its capacity is 50ml up to the given mark. PROCEDURE: Clean the viscometer and dry it thoroughly. Level the viscometer and fill the water bath with water for determining the viscosity at x 0 C. Place the ball valve on the jet to close it and pour the lubricating oil into the cup up to the mark of the indicator. Place a clean kohlrausch flask below, directly in line with discharge jet. Insert a thermometer and a stirrer in the cup and cover it with a lid. Heat the water in the bath up to the desired temperature x 0 C, lift the ball valve and start the stop watch. Oil from the jet flows into the flask. Stop the stopwatch when the lower level of the meniscus touches the mark on the kohlrausch s flask. Record the time taken for 50 ml of the oil to collect in the flask. Repeat the experiment to get the reproduceable results. Let the time taken be t seconds. The viscosity of the oil sample at x 0 C is t Redwood seconds. PRECAUTIONS: The oil sample must be filtered through a muslin cloth to remove solid particles which may clog the jet. RESULT: The viscosity of oil is determined by using Redwood Viscometer. Prepared by T K MOHAN (mohanchemist@gmail.com) Page

21 OBSERVATION AND CALCULATIONS: GRAPH: S.No. Temperature Time flow Mean (viscosity) Trial I Trial II Viscosity Temperature Prepared by T K MOHAN (mohanchemist@gmail.com) Page 21