Discussion Overview
The discussion revolves around the preparation of a calcium hydroxide (Ca(OH)2) solution with a target pH of 13.2. Participants explore the feasibility of achieving this pH using various additives, including sodium sulfate, sodium chloride, and sodium nitrate, alongside Ca(OH)2 and distilled water. The conversation touches on solubility limits, dissociation fractions, and the effects of ionic strength on pH.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant notes that the solubility of Ca(OH)2 at 25°C is 1.65 g/L, suggesting that achieving a pH of 13.2 may not be possible with just Ca(OH)2 and water.
- Another participant questions the role of sodium sulfate, chloride, and nitrate in altering pH, suggesting that they may only increase ionic strength without significantly affecting pH.
- A participant mentions the possibility of starting with a saturated Ca(OH)2 solution and adding NaOH to reach the desired pH, acknowledging that this may lead to precipitation of calcium.
- One participant expresses skepticism about the suggested method of adding sodium salts, indicating that it seems strange and proposes adding NaOH instead.
- Another participant discusses the distinction between solubility and dissociation fraction, suggesting that sodium salts might react with undissolved Ca(OH)2 to produce NaOH, potentially increasing pH.
- A counterpoint is raised regarding the inability to alter the dissolution equilibrium of Ca(OH)2 by introducing Na+, as it does not change the concentration of OH- ions.
- Further discussion includes the potential for calcium sulfate precipitation or sulfate complexation to affect solubility, but there is disagreement on whether this would still qualify as lime water.
Areas of Agreement / Disagreement
Participants express differing views on the effectiveness of the proposed additives in achieving the desired pH, with no consensus reached on the validity of the suggested method or the role of sodium salts in the process.
Contextual Notes
The discussion highlights limitations related to the assumptions about the interactions between the various salts and Ca(OH)2, as well as the unresolved implications of complexation reactions on pH and solubility.