What is the different b/n change in internal energy(^E) and enthalpy change(^H) ? Under what circumstances are change of internal energy(^E) and enthalpy change(^H)?
Bob Pursley answered your earlier post. Check that response.
Dear DrBob222,Mr bob pursley answer is not enough(clear) for me.please explane briefly two Questions
The difference between change in internal energy (∆E) and enthalpy change (∆H) lies in the quantities they represent and the conditions under which they occur.
Change in internal energy (∆E) is a measure of the energy transferred to or from a system during a physical or chemical process. It accounts for changes in the system's internal energy due to factors such as heat transfer (q) and work done on or by the system (w). Mathematically, it can be expressed as:
∆E = q + w
Enthalpy change (∆H), on the other hand, represents the heat transferred to or from a system at constant pressure. It takes into account the change in internal energy (∆E) as well as the work done on or by the system (∆E). Mathematically, it is given by:
∆H = ∆E + P∆V
where P represents the constant pressure and ∆V is the change in volume.
In simple terms, ∆E considers all forms of energy transfer (heat and work), whereas ∆H specifically focuses on the energy transfer as heat at constant pressure.
Now, under what circumstances do these changes occur?
Change in internal energy (∆E) can occur in any process where a system experiences a change in its internal energy. This can include physical processes like phase transitions (e.g., melting, evaporation) or chemical processes (e.g., reactions) where there is a change in the energy stored within the system itself.
Enthalpy change (∆H), on the other hand, is relevant in processes involving heat exchange at constant pressure, typically referred to as constant-pressure processes. This usually occurs in open systems where there is a free exchange of heat with the surroundings, allowing the system's pressure to remain constant throughout the process. Examples of such processes include reactions taking place in an open container or systems with a constant pressure external to them, such as reactions conducted in open air.
In summary, ∆E represents the overall change in internal energy of a system, considering both heat and work, while ∆H specifically represents the heat transferred at constant pressure. The circumstances for change in internal energy can be any process causing energy transfer within a system, while enthalpy change occurs in processes involving constant-pressure conditions.