Experiment 2 (Determination of Alkalinity in Water) PDF

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Name of experiment:-Determination of Alkalinity in Water...

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Subject:Environmental Engineering Lab -------------------------------------------------------------------------------------------------------------------

Experiment-02 Name of the experiment: Determination of Alkalinity in Water

Aim of the experiment: To determine acid neutralizing capacity of given water sample.

Theory: Alkalinity is the presence of sufficient alkaline ions in water. The absence of alkalinity makes the water acidic. Water is said to be alkaline when pH of water is above 7.00. The determination of alkalinity is very useful in water and waste water because it provides buffering to resist changes in pH value. The alkalinity and acidity in water usually changes in natural waters with large algal growth. The alkalinity of natural waters is primarily due to the salts of week acids and bicarbonates represent the major form of alkalinity. Alkalinity can be expressed as follows: Alkalinity (mol/l) = [HCO3-] + 2[CO3 2-] + [OH-] – [H+] The presence of alkalinity in surface waters is primarily indicates the concentration of carbonate, bicarbonate and hydroxide contents. Alkalinity in excess of Alkaline earth metal concentrations is significant in determining the suitability of a water for irrigation. Alkalinity measurements are used in the interpretation and control of water and waste water treatment processes. Raw domestic waste water has an alkalinity less than or only slightly greater than that of the water supply. Alkalinity of water is the capacity of water to neutralize acid. It is usually expressed as Total Alkalinity or Caustic Alkalinity in water. It is significant in many uses and treatments of natural waters and wastewaters. Alkalinity is measured titrimetrically by titrating against Dilute Sulphuric Acid. Phenolphthalein and Methyl Orange are used as indicator to indicate pH 8.3 and pH 4.3. Phenolphthalein process a pink colour when pH is above 8.3 and colourless when pH is below 8.3. Natural water alkalinity is caused primarily by the presence of weak acid salts, though strong bases (i.e. OH- ) may also contribute in extreme environments. Bicarbonates are the most common type of alkalinity found in natural waters, and they are formed by the partitioning of CO2 from the atmosphere and the weathering of carbonate minerals in rocks and soil. Other salts of weak acids, such as borate, silicates, ammonia, phosphates, and organic bases from natural organic matter, may be present in small amounts. Alkalinity is frequently identified as mg/L CaCO3 because the majority of alkalinity is derived from the weathering of carbonate minerals. Titration with standardized acid determines the total amount of hydroxyl ions in a solution. This is a well-known water-analysis procedure for estimating the concentrations of hydroxyl, carbonate ion, and bicarbonate ions. This titration has two pH endpoints, P and M, which correspond to the phenolphthalein and methyl orange indicators.

Procedure for simulation: 1.Open the simulation of alkalinity of water and click on the arrow mark shown at the bottom

right corner. 2.Click on the funnel to place it on the burette. 3.Click on the lid to open and click on the bottle to pour dilute sulphuric acid on to the burette up to zero mark. 4.Remove the funnel by clicking on it. Click on the NEXT button once the funnel is removed. 5.Squeeze the pipette bulb by clicking on it and press the up arrow to take the Na2CO3 solution up into the pipette. 6.Press the down arrow on the pipette bulb to release liquid into the conical flask. 7.Note the addition of 10ml 0.02N Sodium carbonate solution to conical flask. Click on NEXT button. 8.Click on the dropper to add methyl orange indicator to the conical flask. 9.After the addition observe the change in colour of the solution, then click on the NEXT button. 10.Click on the knob to add the dilute sulphuric acid into the conical flask. 11.Observe the colour change of the solution in the conical flask to wine red. Click on the NEXT button. 12.Calculate Normality of Sulphuric acid using the formula and enter the value then click on CHECK button to check the result. 13.Repeat the same procedure for the 100ml of water sample and note down the observation. Calculate the alkalinity of water using the formula and enter the value then click on CHECK to check the result.

Precautions: 1.Always wear lab coat and gloves when you are in the lab. When you enter the lab, switch on the exhaust fan and make sure that all the chemicals and reagents required for the experiment are available. If they are not available, prepare the reagents using the components for reagent preparation. 2.Properly adjust the flame of the Bunsen burner. The proper flame is a small blue cone; it is not a large plume, nor is it orange. 3.Make sure to clean all your working apparatus with chromic acid and distilled water and ensure that all the apparatus are free from water droplets while performing the experiment. 4.Make sure to calibrate the electronic weigh balance before taking the measurements. 5.Clean all glassware with soap and distilled water. Once the experiment is completed, recap the reagent bottles. Switch off the light, exhaust fan and gas cylinder before leaving the lab....