Alkalinity Lab

846 Words 4 Pages
Alkalinity is a measure of the ability of a water to resist changes in pH. Alkalinity in water is due to the presence of weak acid systems that consume by hydrogen ion produced by other reactions, allowing chemical or biological activities to take place within a water without changing the pH (1). In this way the alkalinity protects aquatic life.
The measured value may vary considerably with the end-point pH used. Alkalinity is a measure of an aggregate property of water and can be interpreted in terms of specific substances only when the chemical composition of the sample is known (2).
Alkalinity is an important parameter in various applications and treatments of natural waters and wastewaters. The amount of alkalinity is taken into consideration
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The four methods used for quantification of alkalinity (4) are summarized below:
•Use of a pH indicator: a change in the color from pure yellow to orange is observed and recorded when a known pH is reached. In this his experiment we used methyl orange as indicator The consumed volume until specific pH allow us to know how much volume is required to reach the endpoint.
•Visual identification from titration curve; the data are recorded after that small volume are added from buret until endpoint. Then graph pH vs volume added lets us know the volume consumed of titrant and then the alkalinity can be calculate.
•Numerical differentiation of the titration data that method is performed by plotting ∆E/∆V vs the volume of acid added. A maximum in the plot corresponds to the point at which the pH is changing most rapidly (the inflection point).
•Use of the Gran Functions: This method consist of equations through which different areas of the titration curve can be linearized. The result provides information about the endpoint of the
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Calibration of Ph.
To calibrate the pH meter the mV and temperature reading of three pHs 4, 7 and 10 standard buffer solutions are recorded. This reading are obtained using pH meter .The mv reading versus pH are plotted excel to generate a calibration curve, from the equation of the curve generated, the pH for each replicated sample and the analytic solution can be determined.
Task 2. Standardization of HCL.
The titrant solution of 0.02 m HCL and 0.08 M NaCl is standardized using a solution consists of a mixture of 0.05 M Na2CO3 and 0.085 M of NaCl as analytic solution. 50 ml the latter solution is placed into a beaker and pH electrodes are immersed into the solution to read the electrode potential (mV). Two drops of indicator methyl orange are added to the solution. Detailed data is collected by adding small volume of acid titrant and recording the corresponding to the two equivalence points.
Task 3 Alkalinity of natural water. 10 mL of 0.1M NaCl solution is added in a100 mL volumetric flask using natural water as diluent.
Tree replicate of 50 ml of this sample is transferred into a beaker, and the same steps used to standardization are followed for each sample.
Task 4: Alkalinity of natural water using Hach

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