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Lab #4: pH, Alkalinity, Acidity, Calcium, Conductivity

Lab #4: pH, Alkalinity, Acidity, Calcium, Conductivity. Alkalinity. Calcium. Lake Function. Joe Conroy 20/21 April 2004. pH. Acidity. Conductivity. Goals. Measure pH, alkalinity, acidity, calcium, and conductivity in three water sources

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Lab #4: pH, Alkalinity, Acidity, Calcium, Conductivity

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  1. Lab #4: pH, Alkalinity, Acidity, Calcium, Conductivity Alkalinity Calcium Lake Function Joe Conroy 20/21 April 2004 pH Acidity Conductivity

  2. Goals • Measure pH, alkalinity, acidity, calcium, and conductivity in three water sources • Determine how these parameters interact to shape lake function • Gain familiarity in lab analytical techniques

  3. pH • Measure of the hydrogen ion concentration • pH = -log[H] • Use either color indicators or electrodes • Electrode system description on pp. 126-127

  4. Alkalinity • Buffering capacity of lake waters • Due to dissolved substances that accept protons • Carbonate species important • Amount of carbonate present dependent on pH, watershed, partial pressure of CO2 in atm. CO2(atm)CO2(dis)+H20H2CO3H++HCO3-H++CO32- • In practice, Alkalinity = acid added to equivalence point standardized to CaCO3

  5. Acidity • Opposite of Alkalinity • Determines the amount of CO2 dissolved in lake water • Acidity = base added to equivalence point • Selection of acid or base of the appropriate normality simplifies calculations (pp. 131-132)

  6. Calcium • Important for determining the “hardness” of lake water • Hardness determines the ability of water to precipitate soap • Expressed in terms of CaCO3/L • Determined using Sodium EDTA titration

  7. Specific Conductance • Measure of the dissolved ions in a lake water sample • Equal to the inverse of the resistance • Temperature of importance (inc. of 2-3%/°C) • Use a conductivity meter • Standardized to 25°C and to a standard KCl solution

  8. Consequential Questions • How do alkalinity, acidity, and pH interact to determine the total dissolved inorganic carbon in a lake? • How do phytoplankton (who are taking up C for photosynthesis) affect the alkalinity? • How does calcium affect carbon concentration and phytoplankter processes?

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