Discussion Overview
The discussion centers around the role of solids in equilibrium expressions, particularly why the concentrations of pure solids are not included. Participants explore the implications of solid concentration in reactions and the concept of activity in equilibrium calculations.
Discussion Character
- Debate/contested
- Conceptual clarification
- Technical explanation
Main Points Raised
- One participant questions the reasoning that the concentration of a pure solid is constant, suggesting that if a solid dissociates, its concentration should change.
- Another participant introduces a scenario involving a nail dropped into a solution, questioning whether it reacts and what its concentration would be.
- A follow-up post speculates that the size of the solid affects its concentration change, proposing that smaller amounts of solid might significantly impact the original mass.
- Another participant counters that the size is not the critical factor, emphasizing that reactions occur only at the surface of the solid.
- A further inquiry raises the issue of how a solid that dissolves significantly can still be considered to have a constant concentration when only a small fraction remains.
- One participant notes that concentration is an approximation and explains that the reaction quotient is based on activities, stating that for solids, the activity is always 1.
- It is mentioned that there are various approaches to this problem, which have been discussed previously.
Areas of Agreement / Disagreement
Participants express differing views on the significance of solid concentration in equilibrium expressions, with no consensus reached on the underlying principles or implications.
Contextual Notes
Limitations include the dependence on definitions of concentration and activity, as well as the unresolved nature of how significant changes in solid mass affect equilibrium considerations.