1/8/2024 0 Comments Thermodynamics calculator siIf a reaction adds energy to a system (endothermic), ΔH is positive and if a reaction subtracts energy from a system (exothermic), ΔH will be negative. This merely states that the total energy change after a reaction is equal to how much energy is present at the end subtracted by the amount we started with. In any open system, the following is true: We want to know what the change in enthalpy, ΔH, for a given reaction or process will be. In most thermodynamic applications, total enthalpy is not the quantity of interest. Where H is the total enthalpy, U is the energy of the work done in the system, p is pressure, and V is the volume of the system. This is to be seen as the specific enthalpy version of, and not to be confused with, the enthalpy equation: Where u is the specific energy, p is the pressure and v is the volume. Specific enthalpy can also be written in terms of specific energy, pressure, and specific volume such that the following equation is true: Where h is the specific enthalpy, H is the enthalpy of the system, and m is the total mass of the system. ![]() Specific enthalpy is calculated by taking the total enthalpy of the system and dividing it by the total mass of the system. ![]() ![]() The SI units for specific enthalpy are kJ/kg (kilojoules per kilogram). Specific enthalpy is used in thermodynamic equations when one wants to know the energy for a given single unit mass of a substance. Specific Enthalpy is the total energy in a system due to pressure and temperature per unit of mass in that system.
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