Understanding HCl + Ca(OH)2 Reaction: pH?

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Discussion Overview

The discussion focuses on the reaction between hydrochloric acid (HCl) and calcium hydroxide (Ca(OH)2) in aqueous solution, specifically exploring the chronological sequence of events during the reaction and the resulting pH of the solution. Participants are examining the behavior of ions in solution and the implications for acidity or alkalinity.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that H+ ions will combine with OH- ions to form water, questioning the behavior of Cl- and Ca2+ ions in terms of their impact on pH.
  • Another participant agrees that CaCl2 remains dissociated in solution and notes that it does not significantly affect pH, emphasizing the importance of considering excess reagents.
  • A different participant asserts that both calcium and chloride ions are neutral and that the resultant salt from the reaction is neutral as well.
  • One participant challenges the claim that calcium and chloride ions are sparingly available, stating that calcium chloride is highly soluble in water, which contradicts the previous assertion.

Areas of Agreement / Disagreement

Participants express differing views on the solubility of calcium chloride and its effect on pH, indicating that there is no consensus on these points. The discussion remains unresolved regarding the implications of the ions present in the solution.

Contextual Notes

There are unresolved assumptions regarding the definitions of acidity and neutrality in the context of the ions involved, as well as the solubility of calcium chloride in aqueous solution.

TylerH
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Homework Statement



I'm trying to understand what happens, chronologically, when 2mol HCl is mixed with 1mol Ca(OH)2 in aqueous solution. Also, is the resulting solution acidic or alkaline.

Homework Equations



2HCl + Ca(OH)_2 = 2H^+ + 2Cl^- + Ca^{2+} + 2(OH)^- = ?

The Attempt at a Solution



I think the H ion will combine with the OH's to make water, but I don't know what happens to the Cl and Ca ions. If they remain unbonded and just float around in the water, then I don't know what effect this has on pH. They don't donate H, obviously, but they don't covalently bond with it either.
 
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You are right - CaCl2 stays dissociated and doesn't affect pH (well, to some extent it does, but that's most likely not important here). Think just in terms of excess reagent.
 
Calcium and Chloride ions are present in aqueous solution (Corrected). Chloride Ions are neutral, so are Calcium ions.

We can also see it as a strong acid HCl reacting with Ca(OH)2, which is also quite strong, so the resultant salt is quite neutral.
 
Last edited:
AGNuke said:
Calcium and Chloride Ions are sparingly available as ions themselves, instead, they form insoluble salt, which is precipitated.

Please elaborate, what you wrote doesn't make much sense to me. Calcium chloride is quite soluble, tens of grams in 100 mL of water (even more than NaCl).
 

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