What is Enthalpy?
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the sum of the internal energy of a body or system and the product of its volume multiplied by the pressure.
Enthalpy is a thermodynamic property that measures the total energy of a system, including both its internal energy and the energy required to perform work. It is denoted by the symbol H and has units of energy, usually joules (J) in the International System of Units (SI).
To understand how to calculate or determine the value of enthalpy, you need to consider the following steps:
1. Understand the concept of internal energy: Enthalpy is closely related to a system's internal energy, which represents the total energy of its microscopic constituents, such as atoms and molecules.
2. Recognize the different types of energy involved: Enthalpy takes into account not only the internal energy but also the energy associated with changes in pressure and volume. This additional energy is known as the flow energy or flow work.
3. Determine the enthalpy change: Enthalpy change (∆H) can be calculated when the initial and final states of a system are known. The formula to calculate ∆H is: ∆H = Hfinal - Hinitial, where Hfinal and Hinitial are the enthalpies of the system at the final and initial states, respectively.
4. Consider various processes: Enthalpy can be measured or calculated for different processes, such as chemical reactions, phase changes, and physical transformations. Each type of process requires different considerations and calculations for determining the enthalpy change.
5. Use enthalpy data: In chemistry, enthalpy data is often tabulated in reference books or databases. These tables provide standard enthalpy values for various substances and reactions. By using these values, you can calculate the enthalpy change for a given reaction or process.
It's important to note that while enthalpy is a useful concept in thermodynamics and chemistry, it is not directly measurable. Instead, changes in enthalpy (∆H) can be determined experimentally or calculated based on known data and equations.