ENGINEERING CHEMISTRY LABORATORY MANUAL

Transcription

1 ENGINEERING CHEMISTRY LABORATORY MANUAL For COMMON TO ALL BRANCHES (CSE, ECE, ME, CIVIL, EEE & IT) ADITYA INSTITUTE OF TECHNOLOGY AND MANAGEMENT (AN AUTONOMOUS INSTITUTE) (Approved by AICTE, Accredited by NBA & NAAC, Recognized Under 2(f), 12(B) by UGC Permanently Affiliated to JNTUK, Kakinada) K.KOTTURU, TEKKALI , SRIKAKULAM Dist. (A.P) 1 P a g e

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3 AR-18 Aditya Institute of Technology and Management (Autonomous), Tekkali I Year B. Tech (1 st Sem. EEE, CSE & IT and 2 nd Sem. ECE, ME & CE) CHEMISTRY LABORATORY (Common to All Branches) Subject Code: 18BSL102 Internal Marks: 25 Credits: 1.5 External Marks: 50 Course Objectives: The students will become familiar and understand about: Measure molecular/system properties such as kinematic viscosity, acid number of lubricating oil, etc Measure molecular/system properties such as surface tension, viscosity, ph, conductance of solutions, redox potentials, etc Measure molecular/system properties such as chloride content, hardness of water, dissolved oxygen, iron by colurimeter etc. Synthesize a small polymer molecule and analyze a salt sample. Estimate iron (by colurimeter), partition coefficient, adsorption of acetic acid by charcoal etc. Course Outcomes: The students will learn to: Measure molecular/system properties such as kinematic viscosity, acid number of lubricating oil, etc. Measure molecular/system properties such as surface tension, viscosity, ph, conductance of solutions, redox potentials, etc Measure molecular/system properties such as chloride content, hardness of water, dissolved oxygen, iron by colurimeter etc. Synthesize a small polymer molecule and analyze a salt sample. Estimate iron (by colurimeter), partition coefficient, adsorption of acetic acid by charcoal etc. LIST OF EXPERIMENTS: Choice of experiments from the following: 1. Determination of surface tension and viscosity 2. Determination of Hardness of water sample by EDTA Method. 3. Conductometric estimation of Acid by Base. 4. Conductometric estimation of mixture of acids by base. 5. Potentiometric Titrations. 6. Synthesis of a polymer/drug. 7. Determination of acid value of an oil 8. Chemical analysis of a salt 9. Determination of Dissolved Oxygen present in the given water sample by Modern Winkler s Method 10. Colurimetric estimation of iron 11. ph metric titrations 12. Determination of the partition coefficient of a substance between two immiscible liquids 13. Adsorption of acetic acid by charcoal Use of the capillary viscosimeters to the demonstrate of the isoelectric point as the ph of minimum viscosity for gelatin sols and/or coagulation of the white part of egg 14. Thin layer chromatography. 3 P a g e

4 15. Determination of Chloride content present in given water sample. 16. Determination of kinematic viscosity of given lubricating oil. TEXT BOOKS: 1. Practical Engineering Chemistry by K.Mukkanti, etal. B.S.Publications, Hyderabad (2011). 2. Lab Manual on Engineering Chemistry by Sudharani, Dhanpat Rai Publications, Co., New Delhi., (2009). REFERENCE BOOKS: 1. Engineering Chemistry Lab Manual by Shuchi Tiwari (2010), SCITECH Publications. 2. Vogel s Text Book of Quantitative Chemical Analysis, 6th Edition by G. J. Jeffery, J. Bassett, J. Mendham, R.C. Denney, Longman Scientific & Technical Publications, New York. 3. A Text Book of Engineering Chemistry by R. N. Goyal and H. Goel, Ane Books (P) Ltd.(2009). 4. A Text Book on experiments and calculations Engineering by S.S. Dara, S.Chand & Company Ltd. (2003). 5. Instrumental methods of Chemical Analysis, Gurudeep R, Chatwal Sham, K. Anand, Latest Edition (2015), Himalaya Publications. 4 P a g e

5 CYCLE-I EXPERIMENTS Expt. No. Experiment Page No. 01 Determination Of Dissolved Oxygen Present In The Given 7 Water Sample By Modern Winkler s Method. 02 Determination Of Acid Number Of Given Lubricating Oil Determination Of Strength Of A Strong Acid By ph Metric 15 Method. 04 Conductometric Determination Of Strength Of An Acid 19 Using Strong Base. 05 Determination Of Total Hardness Of Water Sample By 23 Using EDTA Method. 5 P a g e

6 Observations & Calculations: Step-1: Standardisation of Sodium thiosulphate soludion: Burette : Sodium thiosulphate solution. Conical flask : Standard K2Cr2O7 + 10% KI + H 2 SO 4 Indicator : 2 ml starch solution End Point : Blue to colourless S.No. 1 Volume of Potassium dichromate (ml) Burette readings (ml) Initial Final Volume of Hypo Rundown (V ml) 2 3 Potassium dichromate Sodium thiosulphate N 1 = N 2 = V 1 = V 2 = N1V 1 N 2 = V =.. N 2 6 P a g e

7 EXPERIMENT NO - 1 DETERMINATION OF DISSOLVED OXYGEN IN THE GIVEN WATER SAMPLE Aim: To find the quantity of Dissolved Oxygen present in given water sample. Apparatus: BOD Bottles (300ml), Burette, Pipette, Conical Flask, Burette Stand, Wash bottle. Reagents: 0.02N K2Cr2O7, 48% Manganese Sulphate, Alkali-Iodide-Azide Reagent, Starch Indicator, Sodium Thiosulphate, Con. Sulphuric Acid, Sodium Hydroxide, sample water, Distilled water. Principle: Step-1: As the thiosulphate is a secondary standard solution, it has to be standardized by titrating against a primary standard dichromate solution iodometrically using starch indicator. K2Cr2O7 + 6KI + 7H2SO4 Cr2(SO4)3 + 4K2SO4 + 3I2 + 7H2O Step-2: Oxygen present in the water sample oxidizes divalent manganese (Mn 2+ ) to its higher oxidation state (Mn 4+ ) in the presence of Alkali-Iodide-Azide solution. Oxidized manganese liberates iodine from potassium iodide in acidic medium. The amount of Iodine liberated is equivalent to dissolved oxygen present in water sample. The liberated iodine is estimated by titrating with 0.025N hypo using starch as an indicator (wrinkler titration). 2 Mn 2OH 1 2O2 MnO2 H 2O (brown ppt) 2 MnO2 2I 4H Mn 2H 2O I 2 I 2 2Na2S2O3 2NaI Na2S4O6 (Sodium tetrathionate) Formulas: N1V 1 The strength of sodium thiosulphate N 2 = V2 The amount of dissolved oxygen in the given water sample = Titre value x conc. of hypo x 8 x 1000 mg/lit. Volume of sample Procedure: Step-1: Standardisation of Sodium thiosulphate (hypo) solution: 1) Fill the burette with sodium thiosulphate solution. 2) Pipette 10ml of standard potassium dichromate solution into Conical Flask. Add 5 ml of 5 % KI solution and 5 ml of 5N H2SO4 solution. 3) Cover the conical flask with watch glass and put into dark place at 10 min. 4) Titrate the sample solution with thiosulfate until the solution becomes pale yellow. Introduce 5 drops of starch indicator, and titrate with constant stirring to the disappearance of the blue colour. Note down the burette reading. 5) Calculate the normality of Sodium thiosulphate. 7 P a g e

8 Step-2: Determination of Dissolved oxygen in water sample: Burette : Std. Hypo solution (0.025N) Concial Flask : 20 ml water sample consists of liberated Iodine Indicator : 2 ml starch solution End Point : Blue to colorless. S.No. Volume of Water sample (ml) Burette readings (ml) Volume of Hypo Rundown Initial Final (V 3 ml) Dissolved oxygen in the given water sample = V 3 x N 2 x 8 x = = mg /litre 8 P a g e

9 Step-2: Determination of dissolved oxygen present in water sample: 1) Collect 250 ml water sample in a 300ml capacity of BOD bottle. 2) Add 2 ml of manganese sulphate and 2 ml of Alkaline-Iodine-Azide solution. 3) Stopper the BOD bottle immediately. 4) Appearance of brown ppt. indicates the presence of DO. 5) Mix well by inverting the bottle 2 to 3 times and allow the brown ppt. to settle down. 6) Add 2 ml. of conc. H 2 SO 4 solution to dissolve the precipitate. 7) Take 20 ml. of this solution into a clean conical flask. 8) Titrate the liberated iodine with standard hypo solution present in the burette. 9) Add 2 ml of starch solution when the colour of the 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) 12) Repeat the titration till the concordant readings are obtained. 13) Calculate the amount of Dissolved Oxygen in the given water sample by using the formula Result: Source of water sample Dissolved oxygen (mg/l) Marks awarded Signature of the faculty Environmental Significance: 1. The level of dissolved oxygen in fresh water bodies is 8-15 mg/l at 25 0 c 2. If the concentration of dissolved oxygen of water is below 6 ppm, the growth of fish gets inhibited. 3. The dissolved oxygen is used by microorganisms to oxidise organic matter 4. Oxygen depletion helps in release of phosphates from bottom sediments and causes eutrophication. 9 P a g e

10 Observation and Calculation: Step-1: Standardization of KOH Solution. Burette : KOH solution Conical flask : 20 ml. of Oxalic Acid Indicator : Phenolphthalein End point : Colourless to pink. S. No. Vol. of Oxalic Acid Burette readings Initial Final Vol. of KOH rundown Normality of KOH N 2 = N 1 V 1 V 2 N1 V V = Normality of oxalic acid = Volume of the oxalic acid = Volume of the KOH P a g e

11 EXPERIMENT NO-2 ACID NUMBER OF LUBRICATING OIL Aim: To determine the Acid number of lubricating oil. Apparatus: 50 ml burette, 20ml pipette, 250 ml conical flask, 100ml beaker, 250 ml beaker, 50 ml beaker and 50 ml measuring jar. Chemicals: KOH solution, 0.02N oxalic acid, Oil sample, Phenolphthalein indicator, Ethyl alcohol. Principle: The Acid number of lubricating oil is defined as the number of milligrams of potassium hydroxide required to neutralize the free acid present in 1 g of the oil sample. In good lubricating oils, the acid number should be minimum (<0.1). Increase in acid value should be taken as an indicator of oxidation of the oil which may lead to gum and sludge formation besides corrosion. Since free fatty acids present in the oil react with base, their quantity can be estimated by titrating the known weight of the oil sample dissolved in a suitable solvent with a standard alcoholic solution of KOH to a definite end point Procedure: Step 1: Standardization of KOH RCOOH + KOH RCOOK + H 2 O 20 ml standard oxalic acid solution is pipette out into a 250 ml of conical flask and few drops of Phenolphthalein indicator is added. The above solution is titrated with standard KOH solution taken in the burette until the solution changes from colorless to light pink colour The same procedure is repeated until any two readings coincide The concentration of KOH is calculated. 11 P a g e

12 Step-2: Determination of Acid Number: Burette : Std. KOH solution Conical flask : 1gm. of lubricating oil + 5 ml of alcohol. Indicator : Phenolphthalein End point : Colourless to pink. S. No. Vol. of lubricating oil Burette readings Initial Final Vol. of KOH Acid Number of given oil sample is (mg of KOH required to neutralize the acid present in 1 gm of oil) = N 2 Eq. wt of KOH Vol. of KOH N 2 = Normality of KOH Eq. wt of KOH = Vol. of KOH = titer value in the above titration = P a g e

13 Step 2: Determination of Acid Number of given oil sample Result: Name of lubricating oil sample 1 gram (1.1 ml) of oil sample is taken in a 250 ml conical flask and dissolved in 5 ml of Ethyl alcohol. One or two drops of Phenolphthalein indicator is added and the solution is titrated with KOH taken in the burette until the solution changes from colorless to light pink The same procedure is repeated until any two readings coincide The Acid Number of oil sample is calculated. Weight of oil sample Acid number Marks awarded Signature of the faculty 13 P a g e

14 Step-1: Observations & Calculations: Burette : NaOH Solution Conical Flask : 20 ml Oxalic Acid Indicator : Phenolphthalein End Point : Colour less to Pale pink. S.No Calculations: Volume of Oxalic acid (v 1 ml) Burette readings (ml) Initial Final Volume of NaOH Rundown (v 2 ml) Oxalic Acid: M 1 = Molarity of Oxalic Acid = 0.2M V 1 = Volume of Oxalic Acid = 20 ml n 1 = Moles of Oxalic Acid = 1 Sodium Hydroxide: M 2 = Molarity of NaOH =? V 2 = Volume of NaOH = n 2 = Moles of NaOH = 2 Molarity of NaOH = M 14 P a g e

15 EXPERIMENT-3 ph METRIC ESTIMATION OF ACID BY BASE Aim: To determine the Amount of unknown acid solution with standard base solution by ph metric method. Apparatus: ph Meter, Glass membrane electrode, 100ml Beaker, Burette, Volumetric Flask, Glass Rod. Chemicals: Stock acid solution, 0.2 M oxalic acid and Stock base solution. Principle: When a glass surface is in contact with a solution it acquires a potential which depends on H + ion concentration of solution. This observation which has been made by Haber is now used as basis of method of determining the ph of a solution where other electrode cannot be used. The glass electrode has attained much attention in recent years because it can be used almost in all solutions except those which are strongly acidic or strongly alkaline. It has been observed that potential difference exists at the interface between glass and solution containing H + ions. The magnitude of the difference of potential for a given variety of glass varies with its ions concentration at 25 0 C given by: E = E log [H + ]; E 0 = A constant for the given glass electrode. Formula: H 2 C 2 O NaOH HCl + NaOH Na 2 C 2 O 4 + 2H 2 O NaCl + H 2 O Procedure: Step 1: Standardization of sodium hydroxide by using oxalic acid 1. Rinse and fill the burette with the given NaOH solution 2. Pipette out 20 ml of 0.2 M oxalic acid solution into a clean conical flask 3. Add 1 or 2 drops of phenolphthalein indicator to oxalic acid solution. 4. Titrate the solution against sodium hydroxide solution drop wise with shaking till the solution changes to pale pin 5. Note the volume of NaOH used. It is the end point 6. Repeat the titration until the concordant readings are obtained 7. Calculate the molarity of NaOH by using the formula mentioned above Step 2: Determination of molarity of unknown HCl by using standard NaOH through ph metric titration 1. Rinse and fill the burette with standard NaOH solution 2. Now you collect unknown acid in 100 ml volumetric flak and makeup with distilled water 15 P a g e

16 Step-2: Observations and Calculations: ph Metric titration in between HCl and NaOH VOLUME OF NaOH ADDED ph Calculation of unknown molarity of HCl solution: Sodium Hydroxide: M 2 = Molarity of NaOH = V 2 = Volume of NaOH = n 2 = Moles of NaOH = 1 HCl: M 3 = Molarity of HCl =? V 3 = Volume of HCl = 5ml n 3 = Moles of HCl = 1 Molarity of HCl = M Amount of HCl = grs/l 16 P a g e

17 3. Take 5ml of given unknown HCl solution into 100ml beaker and add 45ml of distilled water. The contents are shaken thoroughly. 4. The glass membrane electrode is dipped into the beaker containing the solution. 5. Initially at 0 Burette reading of NaOH solution, ph of the unknown HCl solution can be measured. 6. Then 0.5 ml of base is added from the burette to the acid solution and on stirring thoroughly the ph of the resultant solution can be noted. 7. The ph is noted every time by the addition of 0.5 ml base and finally you observe the ph jump is between V 1 and V 2 ml. After ph jump you need to note about 10 readings. 8. Plot the graph with the volume of base on X - axis versus ph on Y-axis. Identify the suitable jump which changes the medium from acidic ph to Basic ph. 9. Take the average in-between the jump values and draw a line which intercepts X axis. The intersection point gives value of the equivalence point (End point) of acid and base Report: S.No 1 Given Amount of unknown Acid Reported Amount of unknown Acid % Error Marks Signature of the Faculty 17 P a g e

18 Step-1: Observations & Calculations: Burette : NaOH Solution Conical Flask : 20 ml Oxalic Acid Indicator : Phenolphthalein End Point : Colour less to Pale pink. S.No Calculations: Volume of Oxalic acid (v 1 ml) Burette readings (ml) Initial Final Volume of NaOH Rundown (v 2 ml) Oxalic Acid: M 1 = Molarity of Oxalic Acid = 0.05M V 1 = Volume of Oxalic Acid = 20 ml n 1 = Moles of Oxalic Acid = 1 mole Sodium Hydroxide: M 2 = Molarity of NaOH =? V 2 = Volume of NaOH = n 2 = Moles of NaOH = 2 mole Molarity of NaOH = M 18 P a g e

19 EXPERIMENT-4 CONDUCTOMETRIC ESTIMATION OF ACID BY BASE Aim: To determine the amount of unknown acid solution with standard base solution by conductometric method. Apparatus: Conductivity meter (with cell), burette (10ml), volumetric flask (100 ml), beakers (100 ml), stirrer / glass rod. Chemicals: Stock acid solution, 0.05 M oxalic acid in100ml volumetric flask and Stock base solition. PRINCIPLE: Conductometric titrations works on the principle of Ohm's law. As current is inversely proportional to Resistance (R) and the reciprocal of resistance is termed as Conductance, and its unit is Siemen (mho) cm -1. The electrical conductivity of a solution depends on the number of ions and their mobility. In Conductometric titrations, the titrant is added from the burette, and the conductivity readings are plotted against the volume of the titrant. Upon adding a strong base to the strong acids, the conductance falls until the strong acid is neutralized then raised. Such a titration curve consists of 2 lines which intersect at a particular point, known as the End point or Equivalence point. The method can be used for titrating coloured solutions or homogeneous, which cannot be used with normal indicators. Strong Acid with a Strong Base: For example, in the titration of HCl versus NaOH, the addition of a strong base (NaOH) to a strong acid (Hcl). Before NaOH is added, the conductance is high due to the presence of highly mobile hydrogen ions. When the base is added, the conductance falls due to the replacement of hydrogen ions by the added cation as H + ions react with OH - ions to form undissociated water. This decrease in the conductance continues till the equivalence point. At the equivalence point, the solution contains only NaCl. After the equivalence point, the conductance increases due to the large conductivity of OH - ions. H 2 C 2 O NaOH Na 2 C 2 O 4 + 2H 2 O HCl + NaOH NaCl + H 2 O Formula: Procedure: Step 1: Standardization of sodium hydroxide by using oxalic acid 1. Rinse and fill the burette with the given NaOH solution 2. Pipette out 20 ml of 0.05 M oxalic acid solution into a clean conical flask 3. Add 1 or 2 drops of phenolphthalein indicator to oxalic acid solution. 4. Titrate the solution against sodium hydroxide solution drop wise with shaking till the solution changes to pale pin 5. Note the volume of NaOH used. It is the end point. 6. Repeat the titration until the concordant readings are obtained 7. Calculate the molarity of NaOH by using the formula mentioned above 19 P a g e

20 Observations and Calculations: Conductometric titration in between HCl and NaOH Volume of base added Conductance Corrected conductance C 1 = C[(v+V)/V] Calculation of Unknown molarity of HCl solution: Sodium Hydroxide: M 2 = Molarity of NaOH = V 2 = Volume of NaOH = n 2 = Moles of NaOH = 1 mole HCl: M 3 = Molarity of HCl =? V 3 = Volume of HCl = 25 ml n 3 = Moles of HCl = 1 mole Molarity of HCl = M Amount of HCl = grs/l 20 P a g e

21 Step 2: Determination of molarity of unknown HCl by using standard NaOH through conductometric titration 1. In 100 ml beaker take 25ml of given unknown HCl solution and add 25ml of distilled water. The contents are shaken thoroughly. 2. Now, the conductivity cell is immersed in the beaker and the initial conductance of the solution is taken by stirring the solution and keeping it constant. 3. Then, 0.5 ml portions of base is added from the burette and stirred well. The conductance of the solution for each addition is to be noted. 4. The conductivity is corrected by multiplying with the factor [(v+v)/v], where 'v' is the volume of base added and 'V' is the volume of solution initially taken in the beake 5. Plot the graph with respect to the volume of base consumed versus corrected conductance. From the intersection point on the graph which gives value represents the equivalence points of acid and base. Report: S.No 1 Given Amount of unknown Acid Reported Amount of unknown Acid % Error Marks Signature of the Faculty 21 P a g e

22 Observations & Calculations: Step-1: Standardization of EDTA Burette : EDTA Solution Concial Flask : 20 ml CaCl ml. of Ammonia Buffer Indicator : Erichrome Black-T Indicator End Point : Wine red to Sky Blue. S.No. Volume of CaCl 2 Burette readings (ml) (v 1 ml) Initial Final Volume of EDTA Rundown (v 2 ml) N 1 V 1 = N 2 V 2 Normality of calcium chloride (N 1 ) = 0.02N Volume of calcium chloride (V=) = 20 ml Normality of EDTA (N 2 ) =? Volume of EDTA (V 2 ) = volume of EDTA rundown in ml N 2 = N 1 V 1 /V 2 N 2 = N 22 P a g e

23 EXPERIMENT NO- 5 DETERMINATION OF TOTAL HARDNESS BY EDTA METHOD Sample Details: Area: The water sample was collected from Source: Aim: To estimate the total hardness present in the given water sample. Apparatus: Burette, Burette Stand, Pipette, Conical Flask, Beaker, Wash Bottle, Glazed tile, Glass Funnel. Reagents: EDTA, CaCl 2 (0.02N), Ammonia Buffer (ph=10), Erichrome Black-T (EBT) indicator, Distilled Water. Principle: In alkaline condition, EDTA reacts with Calcium and Magnesium to form chelated complex. Ca and Mg develop winered colour with EBT indicator under alkaline condition. When EDTA is added as titrant, Ca & Mg divalent ions get complexed resulting in a sharp change from wine red to sky blue colour which indicates end point of the titration. The ph for the titration has to be maintained at Ca ph 10 Ca EBT EBT complex 2 Mg Mg Wine red (unstable) Ca ph 10 Ca EBT complex EDTA EDTA complex EBT Mg Mg Wine red (unstable) Stable Sky Blue Procedure: Step-1: Standardization of EDTA 1) Take 20ml. CaCl 2 (0.02N) solution in a clean conical flask. 2) To this add 1 ml. of Ammonia Buffer. 3) Add a pinch / 1 (or) 2 drops of EBT indicator. 4) The solution turns to Wine red colour. 5) Titrate with EDTA till the colour changes from Wine red to sky Blue. 6) Note down the volume of EDTA rundown (v 2 ml). 7) Repeat the procedure till the concordant readings are obtained. Step-2: Determination Total Hardness of water sample 1) Take 20ml. water sample in a clean conical flask. 2) To this add 1 ml. of Ammonia Buffer. 3) Add a pinch / 1 (or) 2 drops of EBT indicator. 4) The solution turns to Wine red colour. 5) Titrate with Std. EDTA till the colour changes from Wine red to sky Blue. 6) Note down the volume of EDTA rundown (v 3 ml). 23 P a g e

24 Step-2: Determination Total Hardness of water sample Burette : Std. EDTA Solution Concial Flask : 20 ml water sample + 1 ml. of Ammonia Buffer Indicator : Erichrome Black-T Indicator End Point : Wine red to Sky Blue. S.No. Volume of Water Burette readings (ml) Volume of EDTA Rundown sample (ml) Initial Final (v 3 ml) Calculation of Total Hardness: = V 3 x N Volume of Sample = mg / litre. Total Hardness is = mg / litre or ppm 24 P a g e

25 Result: Source of water sample Hardness (mg/l or ppm) Marks awarded Signature of the faculty Significance: 1. The permissible limit of total hardness is 200 mg / litre as per W.H.O. 2. Absolutely softwater is tasteless and corrosion in nature. 3. Hardwater causes excessive consumption of soap. 4. Scales are formed in the boilers and reduce the heat efficiency of the boilers. 5. Important in determining the suitability of water for domestic and industrial use. 6. Determination of hardness serves as a basis for routine control of softening process 25 P a g e