Water's Hidden Story: Hardness

Unveiling Water Hardness Through EDTA Titration

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Slide 1: CURE: Introduction

What's Really in Our Water?

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  • Understanding Water Hardness: Water hardness, primarily caused by calcium and magnesium ions, significantly impacts water quality. This investigation focuses on quantifying calcium carbonate levels.
  • Complexometric Titration: Using EDTA, a titrant, we measure the amount required to bind with calcium ions, allowing precise calculation of calcium carbonate concentration in water samples.
  • Experiment's Purpose: The core objective is to accurately determine the concentration of calcium carbonate in various water samples, enabling a detailed comparison and rigorous water quality evaluation.
  • EDTA Role: EDTA, or Ethylenediaminetetraacetic acid, is the main reactant here, binding to metal ions in the solution. Water hardness can be determined by this reaction.
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Slide 2: Key Concepts

Definitions and Equations

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  • Water Hardness: Water hardness refers to the concentration of minerals, mainly calcium and magnesium ions, expressed as calcium carbonate (CaCO₃) in parts per million (ppm).
  • Titration Reaction: The reaction between calcium ions (Ca²⁺) and EDTA (EDTA⁴⁻) forms a complex [CaEDTA]²⁻. This reaction's completion signifies the titration endpoint.
  • PPM Calculation: To calculate ppm CaCO₃: (moles CaCO₃ / volume of solution (L)) × (100.09 g/mol). This helps determine the hardness level in water samples efficiently.
  • Moles Calculation: Moles of EDTA are calculated as: Molarity of EDTA × Volume of EDTA. Due to the 1:1 ratio, moles of CaCO₃ equal moles of EDTA in the titration.
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Slide 3: Procedure Overview

Steps for Accurate Measurement

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  • Preparing Solutions: Diluting a 1000 ppm CaCO₃ solution to create a 200 ppm standard is crucial for accurate calibration and reliable comparison in the titration process.
  • Performing Titration: Titrating water samples with EDTA involves carefully adding EDTA until the endpoint is reached, indicated by a color change, ensuring precise measurement.
  • Recording Data: Meticulously recording initial and final burette readings allows accurate calculation of the volume of titrant used, essential for determining water hardness.
  • Utilizing Hach Strips: Comparing titration results with those from Hach test strips provides a valuable benchmark, helping to validate and refine the precision of the titration method.
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Slide 4: Part 1: Standard Solution

Calculations and Results

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  • Dilution Math: To dilute 1000 ppm CaCO3 to 200 ppm CaCO3, calculate the required volume using V1 = (C2V2) / C1 for accurate concentration.
  • Moles of EDTA: Moles of EDTA are determined using Molarity × Volume. For Trial 1, it's 0.010 mol/L × 0.01005 L = 1.005 × 10⁻⁴ mol ensuring accuracy.
  • Trial 1 Results: Volume of titrant used in Trial 1 was 10.05 mL. This accurate measurement is critical for subsequent calculations of water hardness levels.
  • Trial 2 Values: Volume of titrant used in Trial 2 was 10.12 mL. This consistent measurement is vital for determining water hardness levels.
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Slide 5: Part 2: Natural Sample

Proctor Creek Analysis

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  • Hach Strip Result: The Hach test strip indicated a water hardness of 50 ppm for Proctor Creek Site 6, providing an initial estimate for comparison.
  • Titration Volume: The volume of 1 mM EDTA used in titrating the natural water sample was 31.59 mL, derived from the burette readings.
  • Moles EDTA (Natural): Moles of EDTA calculated: 0.001 M × 0.03159 L = 3.159 × 10⁻⁵ mol. These calculations help determine water hardness effectively.
  • Sample Volume: The natural water sample volume used in the titration was 50 mL, kept constant for precise and accurate hardness determination.
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Slide 6: Titration Data

Known vs. Natural

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  • Known Solution: Initial burette readings were accurately recorded to determine the precise volume of titrant required, ensuring reliable data.
  • Natural Sample: The burette readings, 0.09 mL to 31.68 mL, yielded a volume of 31.59 mL of titrant added, which is essential for calculations.
  • Volume Added: The volumes of titrant added were meticulously recorded, providing essential values for water hardness calculations.
  • Burette Readings: Final burette readings are subtracted from initial values to determine titrant volume, guaranteeing precision in water hardness analysis.
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Slide 7: Calculations: Part 1

Standard Solution Hardness

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  • Moles Titrant: Moles of titrant are determined using molarity and volume, crucial for calculating moles of calcium carbonate titrated in both trials.
  • CaCO₃ Moles: Based on the titration, moles of calcium carbonate are calculated, helping in determination of the water hardness of the provided water sample.
  • Concentration (ppm): Concentration of calcium carbonate is calculated in ppm or mg/L, providing essential water hardness data for the provided water sample.
  • Average Hardness: Average water hardness is determined based on two measurements, ensuring accuracy and minimizing experimental errors in determining hardness.
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Slide 8: Error Analysis

Accuracy Assessment

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  • Relative Error: A relative error of approximately 0.95% indicates high accuracy, validating the reliability of the titration method for measuring CaCO3 concentration.
  • Minor Inaccuracies: Potential errors include reading the burette, incomplete mixing, variations in solution preparation, or losses during transfers.
  • Minimal Impact: The small relative error suggests that these sources had minimal impact on the results, confirming the precision of the titration procedure.
  • Titration Precision: The titration procedure is precise for determining water hardness because minor inaccuracies do not significantly affect final results.
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Slide 9: Calculations: Part 2

Natural Water Sample

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  • Moles of Titrant: Volume of EDTA = 31.68−0.09 = 31.59mL=0.03159, Moles EDTA=0.001×0.03159=3.159×10−5mol in natural water sample for hardness determination.
  • CaCO₃ Moles: Calculating moles of CaCO₃ is crucial to determining the natural water sample's hardness, aiding in effective water quality assessment.
  • PPM Calculation: PPM CaCO₃=0.0503.159×10^−5/0.050×100.09 ≈63.2ppm showing concentration, vital for the overall natural water sample water hardness determination.
  • Concentration Units: Calculating CaCO3 concentration in ppm (mg/L) is key to measuring the water hardness of your natural sample to find water contamination.
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Slide 10: Comparing Methods

Hach vs. Titration

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  • Difference Analysis: Hach test strip results showed 50 ppm, while titration gave 63.2 ppm for water hardness, indicating variations across methods and affecting reliability.
  • Accuracy Insights: Titration's slightly higher value indicates greater precision over the test strip, enhancing overall water quality assessment accuracy and validity.
  • Measurement Evaluation: The titration provides a more accurate measurement than the test strip because it measures different ions in the solution and can measure the color in the solution.
  • Water Hardness: Two values are close, indicating soft water; further analysis needed due to possible ion effects & greater precision of titration methods.
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Slide 11: Water Alkalinity

Neutralization Ability

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  • Alkalinity Defined: Water alkalinity, the capacity to neutralize acids, measures water's ability to counteract acidity, ensuring chemical stability, measured by ppm CaCO3.
  • Neutralizing Acids: Alkalinity is primarily due to bicarbonate, carbonate, and hydroxide ions, crucial in maintaining water's pH balance, reducing pollution effects.
  • Investigating Alkalinity: Alkalinity will be investigated by titrating water samples with 0.002 M H₂SO₄ while monitoring pH changes and using indicators to detect equivalence points.
  • Total Alkalinity: The total alkalinity is calculated from the volume of titrant required to reach the second endpoint and is calculated in terms of calcium carbonate.
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Slide 12: Alkalinity Calculations

Endpoint Calculations

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  • Calculating Volume: The volume of titrant (0.002 M H2SO4) required to reach the endpoint is calculated using 0.0023.0×10^−5 / 0.002 = 0.015L=15.0mL
  • Formula Reminder: To calculate the concentration of CaCO3 based on titrant volume, use: Alkalinity (ppm CaCO₃)= (moles CaCO₃×100.09/sample volume)(L)
  • Moles Calculation: Moles of CaCO₃ are determined through the equation: Moles H₂SO₄=MH₂SO₄ ×V titrant with 1:1 ratio at the second endpoint, water solution stability.
  • Titration Reminder: CaCO3 +H2 SO4 →Ca2++SO42− +H2 O+CO2 This equation can be used for the determination of any CaCO3 with H2SO4.
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Slide 13: Comparing Methods

Alkalinity Differences

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  • Hach Values: Hach-1 test trip results give a water alkalinity of 60 ppm for Proctor Creek Site 6, providing a quick initial approximation of pollution.
  • Alkalinity: 0. 0023.0×10^−5 / 0.002 = 0.015L=15.0mL Calculation helps assess water’s capability to neutralize acids, informing pollution monitoring, for a water sample, this value is given.
  • Alkalinity Results: By finding a value, a comparison with Hach values can be made to calculate the alkalinity of a water sample and calculate water pollution in the water sample.
  • Importance: The importance of all is for water analysis, as water with no contamination is vital for all living species, it is important to find any water pollution.
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Slide 14: Summary of Results

Key Findings

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  • Water Hardness: EDTA titration accurately measured water hardness with minimal relative error, validating this reliable method for precise calcium carbonate quantification.
  • Value: Average hardness was 201.9 ppm, and Hach strip showed 50 ppm; titration is a reliable and accurate way to measure water hardness and find pollution.
  • Titration Importance: Harness the power of titration and understand its application and what the calculation results mean in terms of water sample contamination.
  • Methods: Experiment demonstrates that EDTA titration offers a precise, reliable method for determining water hardness and alkalinity, which is vital for everyone.
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Slide 15: Thank You

Acknowledging Your Participation

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  • Gratitude: Thank you for your attention. We hope this presentation has provided valuable insights into water hardness determination.
  • Acknowledgement: We appreciate your engagement and interest in understanding the importance of accurate water quality analysis.
  • Q & A: If you have any questions, please feel free to ask. We are here to provide further clarification and assistance.
  • Stay Curious!: Keep exploring the fascinating world of chemistry and its applications in our daily lives. Thank you!
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