EC LAB Manual FALL 2018 PDF

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Instructions for performing experiments Non-instrument based experiments: Burette 1. Clean the burette with tap water and then rinse with distilled water 2. Rinse the burette with a small quantity of the solution to be filled in the burette and discard the solution into the sink. 3. Fill the burette with required solution using funnel, remove the funnel and fill the nozzle of the burette with the solution. 4. When the burette reading is noted down, the burette should be at the level of the eye to avoid parallax error. Pipette 1. Clean the pipette with tap water and then rinse with distilled water 2. Rinse the pipette with a small quantity of the solution to be pipetted and discard the solution in to the sink 3. Pipette out exactly 20mL of the solution into a clean conical flask. During transferring the solution into a clean conical flask, when all the solution from the pipette runs out, touch the tip of the pipette to the bottom of the flask gently. Conical Flask 1. Clean the conical flask with tap water and then rinse with distilled water. Test solution 1 Test solution is provided in a small reagent bottle. Transfer the given test solution into a clean 100mL volumetric flask using funnel, after complete transfer of the test solution, add small amount (2-3 mL) of distilled water into the reagent bottle and transfer this solution into the standard flask and finally dilute the solution up to the mark using distilled water with utmost care. Use this as test solution for estimation. 2. Test solution will be provided only one time.

Titration 1. During the addition of the solution from the burette, the conical flask must be constantly rotated with one hand while the other hand controls the stop cock of the burette. Instrument based experiments: 1. Instrument based experiments will be done by a group of students and each group can have maximum of 2 students. 2. The groups will be made as per attendance order or as per faculty’s allotment. 3. Calibration of instruments is not given as part of the procedure and hence students should follow instructions during the lab sessions. 4. Each student in a group should complete the experiment and submit the results.

ENGINEERING CHEMISTRY LAB EXPERIMENTS CHY1701L FALL SEMESTER 2018-19 List of Challenging Experiments S. No Experiment title Water Purification : 1. Hardness estimation by EDTA method and removal by ion-exchange resin 2.

Water Quality monitoring: Total dissolved oxygen assessment in different water samples by Winkler’s method

3.

Estimation of Sulphate for assessing water contamination by conductivity method

4.

Material Analysis: Nickel in Nickel plated component by colorimetry

5.

Iron in carbon steel by potentiometry

6.

Measurement of Retrieved water stored in smart material (hydrogel)

7.

Polymer characterization : Determination of viscosity of different natural polymer/synthetic polymers

8. 9.

10.

Soil analysis by flame photometry: Na/K in soil Ca in water samples Preparation of a working model relevant to syllabus and its demonstration. Examples: 1. Construction and working of electrochemical energy system – students should demonstrate working of the system. 2. Construction of dye sensitized solar cell and demonstration of its working 3. Calcium in food samples

Page No.

WATER PURIFICATION EXPERIMENT-1

Hardness Estimation by EDTA method and its Removal using Ionexchange Resin Date: 1. Introduction to Hard Water and its Classification: Water described as “hard” contains high levels of dissolved Ca 2+ and Mg2+ ions. Ground and surface water dissolve the Ca2+ /Mg2+ containing ores/minerals from surrounding soil and rock and are enriched with these cations. Hardness is most commonly expressed as milligrams of CaCO 3 eq. per litre. Water containing hardness causing species at concentrations below 60 mg/l are generally considered as soft; 60–120 mg/l as moderately hard; 120–180 mg/l, as hard; and more than 180 mg/l as very hard water. Based on the type of anions association with Ca 2+ /Mg2+ ions, the hardness is categorized into permanent (non-carbonate) & temporary (carbonate) hardness. 2. Problems caused by Hard Water: Hard water can cause costly breakdowns in boilers, cooling towers and plumbing. When hard water is heated, the hardness causing salts tend to precipitate out of solution, forming a hard scale or soft sludges in pipes and surfaces, thereby completely plugging pipes and restricting flows. In boilers, the scale prevents efficient heat transfer thereby resulting in energy loss and overheating thereby paving way for serious accidents. At the domestic level, hard water lessens the effectiveness of soap by forming scums/precipitates, which adhere to human skin. Human consumption of water containing excess of Ca and Mg are associated with increased risks of osteoporosis, nephrolithiasis, colorectal cancer, hypertension, stroke, coronary artery disease, insulin resistance, diarrhoea, and obesity. 3. Estimation of Hard Water: Traditionally, hardness in water is estimated by complexometric titration using sodium salt of EDTA and EBT as indicator at pH = 9-10. EBT forms an unstable wine-red coloured complex with Ca2+ /Mg2+ ions, which upon titrating with EDTA, results in the breaking of EBT-Ca 2+/Mg2+ unstable bond and formation of stable EDTA-Ca 2+/Mg2+ bond. The endpoint changes from wine-red (EBTCa2+ /Mg2+ ) to steel blue (free EBT). 4. Modern Treatment of Hard Water: Hard water is made soft by the use of a water softener i.e., ion-exchange resins (IER) which are very small porous spherical polymeric beads, with specific functional groups (sulphonic/carboxylic acid) attached to the polymeric backbone. Therefore, the IERs carrying a negatively charged exchange site can hold a positively charged ion. When the hard water is passed through the resin beads, Ca 2+ /Mg2+ ions are exchanged from the solution for hydrogen/sodium ions, which are much more soluble and does not precipitate out to form scale or sludges. Eventually, the resin beads get saturated with hardness causing ions and the exhausted beads are regenerated by using a mild acid or brine solution to flush out the Ca 2+/Mg2+ ions retained in the resin beads.

Experiment

Problem definition

Methodology Solution Student learning outcomes

Water Purification Hardness Estimation by EDTA method and its Removal using Ion-exchange Resin Hardness of water is due to the presence of dissolved calcium and magnesium salts in water. EDTA forms stable complex with hardness causing salts and is used in the removal of scale and sludge forming impurities in industrial boilers. EBT indicator-Metal ion complex is weaker compared to EDTA-metal ion complex. The end point is the color change from wine red (EBTMetal ion complex) to steel blue (free EBT indicator). Estimation of Calcium hardness (in ppm) in the given unknown sample. Understanding the water softening using ion-exchange resins. Students will learn to a) perform complexometric titration b) understand the efficiency of ion-exchange resins using in water purifiers

Principle: Ehtylenediaminetetraacetic acid (EDTA) forms complexes with a large number of cations including Ca2+ and Mg2+ depending upon pH of solution. Hence, it is possible to determine the total hardness of water using EDTA solution. EDTA in the form of its sodium salt (H 2Y2-) is commonly used in complexometric titration for estimation of metal ion because pure EDTA (H 4 Y) is sparingly soluble in water. EDTA has six binding sites (the four carboxylate groups and the two amino groups) providing six pairs of electrons. The resulting metal-ligand complex, in which EDTA forms a cagelike structure around the metal ion, is very stable at specific pH. All metal-EDTA complexes have a 1:1 stoichiometry. The H2 Y2- form complexes with metal ions as follows. M + H2 Y2- → MY2- + 2H+ ----------- (1) Where, M is Ca2+ and Mg2+ present in water. Reaction (1) can be carried out quantitatively at pH 10 using Eriochrome Black T (EBT) as indicator. EBT forms a wine-red complex with M 2+ ions which is relatively less stable than the M 2+-EDTA complex. On titration, EDTA first reacts with free M 2+ ions and then with the metal-EBT indicator complex. The latter gives a colour change from wine-red to steel blue at the equivalence point.

Removal of hardness using ion-exchange resins: Ion-exchange is a reversible process. When hard water is passed through cation ion-exchange resins packed in a narrow column, Ca 2+ and Mg+ cations in hard water are exchanged with Na+ or H+ ions in the resins. The exhausted resins are

regenerated by passing 10% dil. HCl through the column. A typical example of application is preparation of high-purity water for power engineering, electronic and nuclear industries and in household water purifiers.

Requirements Reagents and solutions: Standard hard water (1mg/mL of CaCO 3 equivalents), 0.01 N EDTA solution, EBT indicator, hard water sample, NH 3-NH 4Cl buffer solution and ion exchange resin. Apparatus: Burette, pipette, conical flask, standard flask burette stand and ion exchange column.

Procedure Titration-I: Standardization of EDTA Pipette out 20 mL of the standard hard water containing 1mg/mL of CaCO 3 (1000 ppm) into a clean conical flask. Add one test tube full of ammonia buffer (NH 4OH – NH4Cl) solution to maintain the pH around 10. Add three drops of Eriochrome Black – T (EBT) indicator and titrate it against the given EDTA solution taken in the burette. The end point is change of colour from wine red to steel blue. Repeat the titration for concordant titre values. Let ‘V 1’ be the volume of EDTA consumed. S. No.

Volume of standard hard water (mL)

Burette reading (mL) Initial

Final

1 2 3 Concordant titer value

Volume of EDTA (V1, mL)

Calculation: 20 mL of given hard water consumes ……………………. (V 1) mL of EDTA 20 mg of CaCO 3 requires ……………………… (V 1) mL of EDTA for complexation ∴ 1 mL of EDTA requires = (20/V 1) …………………….. mg CaCO 3 for complexation This relation will be used in other two titrations Titration-II: Estimation of total hardness of hard water sample Pipette out 20 mL of the given sample of hard water into a clean conical flask. Add one test tube full of ammonia buffer (NH 4OH – NH4 Cl) solution and three drops of Eriochrome Black–T (EBT) indicator. Titrate this mixture against standardized EDTA solution taken in the burette. The end point is the change of color from wine red to steel blue. Repeat the titration for concordant titer value. Let ‘V2 ’ be the volume of EDTA consumed. S. No. Volume of sample hard water (mL)

Burette reading (mL) Initial Final

Volume of EDTA (V2, mL)

1 2 3 Concordant titer value Calculation: From Titration 1, we have the following relation: ∴ 1 mL of EDTA requires = 20/V1 ………………….mg CaCO 3 for complexation From Titration 2, 20 mL of sample hard water consumes = ……………….. (V 2) mL of EDTA. = V 2 x 20/V1 mg of CaCO 3 eq. ∴1000 mL of hard water sample consumes = V 2 x 20/V1 × 1000/20 = V2/V1 × 1000 ppm ∴Total hardness of the water sample = …………………… (“X”) ppm Titration-III: Removal of hardness using ion-exchange method Arrange the ion exchange column on to a burette stand and place a clean funnel on top of the column. Pour the hard water sample (around 40 to 50 mL) remaining after the completion of Titration – 2 through the funnel and into the ion exchange column. Place a clean beaker under the

column and collect the water passing through the column over a period of 10 minutes. Adjust the valve of the column to match the duration of outflow. From the water collected through the column, pipette out 20 mL into a clean conical flask and repeat the EDTA titration as carried out above. Note down the volume of EDTA consumed as ‘V 3 ’. S. No.

Volume of sample hard water (mL)

Burette reading (mL) Initial Final

Volume of EDTA (V2, mL)

1 2 3 Concordant titer value Calculation: From Titration-1, we have the following relation: ∴ 1 mL of EDTA requires = 20/V1 …………………. mg CaCO 3 for complexation From this relation, it can be seen that 20 mL of water sample after softening through the column consumes = ………… (V 3) mL of EDTA. = V 3 x 20/V 1 mg of CaCO3 equiv. 1000 mL of water sample after softening through the column consumes = = V 3 x 20/V1 ×1000/20 = V 3/V1 ×1000 ppm ∴Residual hardness of the water sample = ……………………………. (“Y”) ppm Result: 1. Total hardness of the water sample = ……………………..(“X”) ppm 2. Residual hardness in the water sample = …………………....(“Y”) ppm 3. Hardness removed through the column = ………………………………. (X – Y) ppm Evaluation of Result: Sample number Experimental value

Space for Calculations

Actual Value

Percentage of error

Marks awarded

WATER QUALITY MONITORING EXPERIMENT-2

Total Dissolved Dissolved Oxygen Assessment in Different Water Samples by Winkler’s Method Date: 1. Importance of Dissolved Oxygen (DO): Knowledge of DO concentration in seawater is often necessary in environmental and marine sciences. It is used by oceanographers to study water masses in the ocean. It provides the marine biologist a means to measure primary production, particularly in laboratory cultures. For the marine chemist, it provides a measure of the redox potential of the water column. DO is also an important factor in corrosion. Oxygen is poorly soluble in water. The solubility of oxygen decreases with increase in concentration of the salt and hence, solubility of DO is lesser in saline water. The amount of DO at 100% saturation at sea level is 9.03 mg/L (at 20° C) and is sufficient to sustain aquatic life. Dissolved oxygen is usually determined by Winkler’s method. 2. What is Winkler Method? The Winkler Method is a technique used to measure dissolved oxygen in freshwater systems. DO is used as an indicator of the water body’s health, where higher DO concentrations are correlated with high productivity and little pollution. This test is performed on-site, as delays between sample collections and testing may result in an alteration in oxygen content. 3. How does the Winkler Method Work? Winkler Method uses titration to determine dissolved oxygen in the water sample. A sample bottle is filled completely with water (no air is left to skew the results). DO in the sample is then "fixed" by adding a series of reagents that form an acid compound that is then titrated with a neutralizing compound that results in a colour change. The point of colour change is called the "endpoint," which coincides with the dissolved oxygen concentration in the sample. DO analysis is best done in the field, as the sample will be less altered by atmospheric equilibration. 4. Applications: Dissolved oxygen analysis can be used to determine the health or cleanliness of a lake or stream, amount and type of biomass a freshwater, the amount of DO that a system can support and the amount of decomposition occurring in the lake or stream.

Experiment Problem definition Methodology Solution Student learning outcomes

Water Quality Monitoring: Total Dissolved Oxygen Assessment in Different Water Samples by Winkler’s Method Dissolved oxygen (DO) is essential to living organisms in water but harmful if present in boiler feed water leading to boiler corrosion. DO in water can be assessed using Winkler’s titration method. Estimation of total dissolved oxygen in different water samples. Students will learn to a) perform Winkler’s titration method b) assess the total dissolved oxygen in different water samples

Principle: Estimation of dissolved oxygen (DO) in water is useful in studying corrosion effect of boiler feed water and in studying water pollution. DO is usually determined by Winkler’s titration method. It is based on the fact that DO oxidize potassium iodide (KI) to iodine. The liberated iodine is titrated against standard sodium thiosulphate solution using starch indicator. Since DO in water is in molecular state, as such it cannot oxidize KI. Hence, manganese hydroxide is used as an oxygen carrier to bring about the reaction between KI and Oxygen. Manganese hydroxide, in turn, is obtained by the action of NaOH on MnSO 4.

The liberated iodine (I2) is titrated against standard sodium thiosulphate (Na 2S2O3) solution using starch as indicator.

Requirements: Reagents and solutions: Standard buffer of pH 7, standard KCl solution (0.01 M), standard potassium dichromate (0.01 N), sodium thiosulphate solution, potassium iodide solution, alkali Iodide solution (KI + NaOH in water), conc. H2 SO4 , manganese sulphate, starch solution as indicator. Apparatus: Conical flask, Burette, Measuring flask, Beakers.

Procedure: Titration 1: Standardization of Sodium Thiosulphate The burette is washed and rinsed with sodium thiosulphate solution. Then the burette is filled with given sodium thiosulphate solution. 20 mL of 0.01N K2 Cr2O7 solution is pipette out into a clean conical flask. To this, 5 mL H 2SO 4 and 10 mL of 10% KI are added. This is titrated against sodium thiosulphate solution, when the solution become straw yellow colour, starch indicator is added and then the titration is continued. The end point is disappearance of bluish brown colour. The titration is further repeated twice or thrice to get the concordant value.

Titration 2: Estimation of Dissolved Oxygen 100 mL of water sample is taken in a conical flask. 2 mL of MnSO 4 and 2 mL of alkali iodide solution are added and shaken well for the rough mixing of the reagents. The flask is left aside for few minutes to allow the precipitate to settle down and then 2 mL of conc. H 2 SO4 is added for the complete dissolution of the precipitate. It is further titrated against standard sodium thiosulphate solution. When the solution turn light yellow, starch indicator is added. The end point is the disappearance of bluish brown colour. The titration is repeated twice or thrice to get the concordant value. From the titer value, the strength of dissolved oxygen is calculated. Based on that, the amount of dissolved oxygen in the water sample is calculated. OBSERVATION AND CALCULATIONS Titration - I: Standardization of Sodium Thiosulphate Burette reading (mL) S. No.

Volume of K2Cr2O 7 (mL)

Initial

Final

1 2 3 Concordant value

Calculations: Volume of potassium dichromate V 1 = 20 mL Strength of potassium dichromate N 1 = 0.01 N Volume of sodium thiosulphate V 2 =……………. mL (From Titration – 1) Strength of sodium thiosulphate N 2 = ……………………. ?

Volume of sodium thiosulphate (mL)

V1N1 = V 2 N2 ∴ N2 = V 1N1 /V2 Strength of sodium thiosulphate = N2 = 20 × 0.01/V2

=…………….. N

Titration – II: Estimation of dissolved oxygen S. No.

Volume of water sample (mL)

Burette reading (mL) Initial

Final

Volume of sodium thiosulphate (mL)

1 2 3 Concordant value

Calculation: Volume of sodium thiosulphate V 2 = …………………. mL Strength of sodium thiosulphate N 2 = …………….. N (From Titration – 1 calculation) Volume of water sample taken V 1= 100 mL Strength of given water sample N 1 = ………………… ? V1N1 = V2 N2 N1 = V2 X N2 /100 = ……………….. N Amount of dissolved oxygen (ppm) = normality × equivalent weight of O 2 × 1000 mg/L of the given water sample. = ………………. N × 8 × 1000 mg/L = ------------------ ppm. Result: Amount of dissolved oxygen in the given water sample = …………….. ppm. Evaluation of Result: Sample number

Experimental value

Actual Value

Percentage of

Marks

error

awarded

EXPERIMENT-3

Estimation of Sulphate for Assessing Water Contamination by Conductivity Method Date: Introduction Sulphate (SO42-) is found in almost all natural water. Origin of most sulphate compounds is the oxidation of s...