What is the different b/n internal energy(^E) and enthalpy(^H)? Under what circumstances are internal energy and enthalpy nearly equal?
internal energy: stored in bonds and mass.
enthalpy: that portion of internal energy which can be released (or absorbed) during a chemical reaction.
What is the different b/n change in internal energy(^E) and enthalpy change(^H)? Under what circumestance are change in energy(^E) and enthalpy change(^H) nearly equal? Thanks for your helps.
The difference between internal energy (ΔE) and enthalpy (ΔH) lies in their definitions and the quantities they consider.
Internal energy (ΔE) is a measure of the total energy within a system, which includes the kinetic and potential energies of its particles. It takes into account the energy transfer that occurs as work (w) and heat (q). Mathematically, ΔE = q - w, where q is the heat transferred to the system and w is the work done by the system.
Enthalpy (ΔH) is the total heat content of a system at constant pressure. It considers the energy transfer as heat (q) at constant pressure (P) in addition to the work (w). Mathematically, ΔH = ΔE + PΔV, where P is the constant pressure and ΔV is the change in volume.
When comparing internal energy (ΔE) and enthalpy (ΔH), it is important to note that they are not always equal. The reason for their potential difference is the presence or absence of work done against or by the system, which affects enthalpy but not internal energy. If there is no pressure-volume work involved in a process, then ΔH will be equal to ΔE.
Under circumstances where a system is at constant volume (ΔV = 0), the change in enthalpy (ΔH) and change in internal energy (ΔE) will be nearly equal. This is because when volume remains constant, there is no work done against or by the system, so the only energy transfer is in the form of heat. In such cases, the only difference between ΔH and ΔE will be the difference in the heat transferred.
In summary, internal energy (ΔE) represents the total energy within a system, considering work and heat, while enthalpy (ΔH) accounts for the heat content of a system at constant pressure, including work and heat. They are nearly equal when the system undergoes a process at constant volume (ΔV = 0), where the only energy transfer is through heat.