ENV3001Lspring24Prelab_Week09_WaterAlkalinity

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St. Thomas University *

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2045

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Civil Engineering

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Apr 3, 2024

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Florida International University-Department of Civil and Environmental Engineering ENV3001L: Environmental Engineering Lab I Spring 2024 EXPERIMENT #5: Determination of different forms of alkalinity in water samples by titration with a standard acid solution Pre-Laboratory Assignment Student Name: _____________________________ PID#: ________________ DATE: ________________ Instructions: Read corresponding pages from the Manual. Watch videos posted on Canvas Module for this week’s experiment. As appropriate, use and highlight key concepts defined in the Manual, explain reasoning, show explicit dimensional analysis. Answer each question in the space provided. 1) The Method APHA 2320 is a titration analysis for Alkalinity to determine hydroxide (OH - ), carbonate (CO 3 2- ) and bicarbonate (HCO 3 - ) forms of alkalinity in water. What are two major similarities and two major differences compared to the titration method used in Experiment #3? 2) Give the definitions of the “Palkalinity” and “Talkalinity” titration endpoints that apply to the procedure used in this Experiment. Use words to explain how the titration endpoints are identified. Give the mathematical expression that communicates what Palkaliny volume and Talkalinity volume are in terms of the analytes each of these volumes represents. 3) Read the Manual. In the context of Experiment #5, if you add a few drops of phenolphthalein indicator to a sample and it remains colorless what can you conclude about this sample? Explain

4) A student analyzed a sample of water collected from a lake at the FIU Maidique Campus to assess its alkalinity and buffering capacity using the APHA 2320 method. To perform this analysis, the student measured a 60 mL portion of the water sample and followed the step-by-step procedure in the Manual page 33. The titration was conducted using a standardized solution of hydrochloric acid (HCl) with a concentration of 0.0321 M. The student observed the phenolphthalein indicator changing from magenta to colorless after adding 2.00 mL of the titrant. Subsequently, added a few drops of methyl orange to the same sample and proceeded with the titration until the color change from orange to salmon was noticed. The student recorded the volume of titrant consumed from the first to the second indicator color change as 8.00 mL. (a) For accurate interpretation of the results of APHA 2320 it is necessary to record the P- and T-alkalinity volumes correctly. In this case, what are the P- and T-alkalinity volumes? Did the student record the vales correctly? (b) Use Table 5.1 to identify which forms of alkalinity exist in the sample and determine the volume of the titrant that was consumed to neutralize these forms. (c) Apply the correct pair of equations (Equations 5.3a, 5.3b or Equations 5.4a, and 5.4b) to convert the volume of titrant associated with each analyte into concentration units expressed in milligrams per liter (mg/L) as calcium carbonate (CaCO 3 ). (d) If instead of HCl, 0.0321 M sulfuric acid is used as titrant, what volume of titrant would be consumed to reach the equivalent point of a 50 mL of the water sample? 5) Health and safety. Use information for 0.05 M H 2 SO 4 posted on the Canvas Module. H=Health, F=Fire, R=Reactivity NFPA (H,F,R) NFPA Health Hazard Rating Description and Personal Protection

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