CE 256 Lab 4 Report

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New Mexico State University *

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256L

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Civil Engineering

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Apr 3, 2024

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Alkalinity and Acidity Lab #4 CE 256L M02 Lab Date: 10/05/22 Report Due: 10/12/22 Group Members: Louis Mauriot, Cristian Sanchez, Omar Saucedo, Cristina Esquivel, Brittany Hymer

Table of Contents INTRODUCTION ........................................................................................................................................... 1 PROCEDURE ................................................................................................................................................. 1 RESULTS ....................................................................................................................................................... 2 DISCUSSION ................................................................................................................................................. 3 REFERENCES ................................................................................................................................................ 3 APPENDIX .................................................................................................................................................... 4 List of Tables Table 1: Alkalinity Titrations Table 2: Acidity Titrations List of Figures Figure 1: Alkalinity Equation Figure 2: Acidity Equation Figure 3: Sample Calculation of Alkalinity Figure 4: Sample Calculation of Acidity

INTRODUCTION The reaction of a strong acid with alkaline water to increase pH to a designated point can be defined as the ability of water to neutralize acids or simply put: the alkalinity of water. Carbonates (CO 3 2- ), hydroxides (OH - ) and bicarbonates (HCO 3 - ) are among the most common contributors to alkalinity in natural waters. Other contributors include but aren’t limited to silicates, phosphates or slats of weak acids. The ability to neutralize a base can be defined as the acidity of water. The most common case of biological oxidation of organic matter such as polluted water is caused by the presence of carbon dioxide (CO 2 ). This process contributes most acidity to natural water. Consequently, high corrosiveness can be found in most waters containing carbon dioxide. Titration is a common method to determine alkalinity volumetrically. There are two alternate methods to determine the end point. One is with the help of an acid and an indicator. The other method consists of using a pH meter. Titration with the assistance of a base can also be used to determine acidity. PROCEDURE Since alkalinity and acidity consist of two different experimental processes, we will be conducting two separate experiments to test each procedure. Alkalinity is the first experimental procedure. The initial step consists of pouring an amount of tap water within the range of 50-100ml into a beaker. With the help of a graduated cylinder, we record the exact volume of tap water. The indicator we used here was methyl orange. We add 3-4 drops of this latter to our tap water solution. Bromocresol green was an alternate indicator that could’ve been used. However, the recommended indicator to use for this lab was methyl orange. We use a 50ml beaker to gather a fair amount (about 50ml) of 0.02 N H 2 SO 4 . This latter is then poured into a burette. Our tap water and indicator solution is then poured into an Erlenmeyer and placed under the burette. The titration process can now begin. The endpoint is when the solution reaches a very slight pink color. The pH is also checked consistently to verify it ranges approximately 4.3. Once complete, the final pH and amount of titrated acid is recorded. The experimental procedure is repeated 2-3 times with tap water. We then switch over to pond water and repeat the entire process. All data is recorded in a table (refer to table 1 below) and the total alkalinity is calculated. Acidity is the second experimental procedure and follows an almost identical process. However, we only perform the experiment on tap water since the pH wouldn’t change for pond water. This time the color indicator changes to phenolphthalein. We add about 5 drops. This doesn’t affect the color of the solution initially. The titration process is executed until the solution turns bright pink which is the endpoint. The pH is measured and recorded. The amount of base titrated is also recorded (refer to table 2 below) and the total acidity is calculated.

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