Discussion Overview
The discussion revolves around the heat of reaction in thermodynamics, specifically comparing the heat of reaction at constant pressure and constant volume for a given chemical reaction at 298 K. Participants explore the definitions and implications of state functions, internal energy, and enthalpy in this context.
Discussion Character
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- One participant attempts to calculate the difference between heat of reaction at constant pressure (ΔHp) and at constant volume (ΔHv) using the relationship ΔHp = ΔUp + PΔV and questions the equality of ΔUp and ΔUv.
- Another participant asserts that ΔU is a state function and is zero for a process between two states, suggesting that ΔUp = ΔUv.
- Some participants argue that since ΔH is a state function, ΔHp should equal ΔHv, questioning why this is not the case.
- There is a discussion about the thermodynamic state variables that determine internal energy for an ideal gas and how they relate to constant pressure and constant volume processes.
- Several participants clarify that ΔH is defined as the enthalpy change at constant pressure and that the terms ΔHp and ΔHv are not standard, suggesting that Qp and Qv might be more appropriate terms.
- One participant notes that while ΔH can be calculated for processes not at constant pressure, it is conventionally defined at constant pressure.
- There is a mention that performing a reaction at constant temperature does not yield the same final state as at constant volume, affecting the final pressure and volume.
- A participant questions whether Δ(PV) equals zero for the reaction at constant volume.
- The discussion touches on the procedure for measuring the heat of reaction, emphasizing the importance of maintaining constant temperature and pressure during the measurement process.
Areas of Agreement / Disagreement
Participants express differing views on the relationship between ΔHp and ΔHv, the definitions of ΔH, and the implications of state functions. There is no consensus on whether ΔHp equals ΔHv, and the discussion remains unresolved regarding the definitions and calculations involved.
Contextual Notes
Participants highlight potential confusion regarding the definitions of ΔHp and ΔHv, as well as the conditions under which ΔH is calculated. There are also unresolved questions about the behavior of state functions in different thermodynamic processes.