Alkalinity Expressed as pOh and Henrys Law Questions

# 5 Acids & Bases II, Titrations & Buffers 

  1. What is the alkalinity and pH of a solution containing 0.0001 M NaHCO3 after it has reached an equilibrium with an underground atmosphere containing CO2 at a partial pressure of 0.01 atm?
  2. Some groundwater water is equilibrated with PCO2 = 10-2.0 atm. The solution needs to be adjusted to pH

8.0 by the addition of NaOH or HCl. What, in fact, would need to be added and in what dosage (mg/l)?

  1. A water is characterized by a pH of 8.3 and an alkalinity of 25 mg/l as CaCO3. It is desired to increase the alkalinity to 125 mg/l as CaCO3 while not changing pH. Describe two possible means to accomplish this objective by the addition/removal of chemical(s). Summarize initial and final water characteristics as well as chemical type(s) and dosage(s).
  2. A NH stream flows at 2.0 MGD with a pH of 6.2 and a total alkalinity of only 50 mg/l as CaCO3. A process wastewater discharge (1.0 MGD and pH of 2.5) is added to the NH stream. (a) Will the resulting pH of mixing the wastewater discharge with the stream result in the pH falling below 6.0? (b) If so, describe at least two different treatment scenarios that could be used to raise the mixture pH to a desired target of 8.0. Please provide both the chemical(s) and dosages required.
  3. Develop a titration curve for a 0.01 M H2CO3 solution using NaOH as the titrant. At what pH(s) would the solution be most resistant to pH changes? Hint: Use Excel to develop a f vs pH graph following the equation provided in the class notes.
  4. A buffer solution has been prepared by adding 0.2 M of HAc and 0.1 M of NaAc. The pH of the solution has been adjusted to 5.0 by addition of NaOH. How much additional NaOH (mg/l) is required to increase the pH to 5.3? (Try to solve this problem using the Buffering Capacity Index equation)
  5. A 1-liter solution contains 100 mg of HCl. Calculate the following:
      1. Initial pH
      2. pH after addition of 1 ml of 1.0 N NaOH.
      3. pH after addition of 2 ml of 1.0 N NaOH
      4. pH after addition of 3 ml of 1.0 N NaOH

 

 

 

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