δh = q - w_{shaft}

Definition

The equation $$\delta h = q - w_{shaft}$$ represents the change in enthalpy of a system, where $$q$$ is the heat added to the system and $$w_{shaft}$$ is the work done by the system on its surroundings. This equation is a direct expression of the First Law of Thermodynamics, illustrating the relationship between heat transfer and work in chemical processes. Understanding this relationship is essential for analyzing energy changes in chemical reactions and various engineering applications.

5 Must Know Facts For Your Next Test

1. The term $$\delta h$$ represents a differential change in enthalpy, indicating how energy content changes as a result of heat and work interactions.
2. In processes where no shaft work is done, the equation simplifies to $$\delta h = q$$, meaning all heat added contributes directly to the change in enthalpy.
3. This equation helps engineers and chemists calculate how much heat must be supplied or removed during reactions to maintain desired temperatures or pressures.
4. When dealing with phase changes, such as melting or vaporization, understanding $$\delta h$$ allows for accurate predictions of energy requirements for such transformations.
5. This relationship is crucial in designing reactors and heat exchangers, as it aids in optimizing thermal efficiency and energy recovery processes.

Review Questions

• How does the equation $$\delta h = q - w_{shaft}$$ illustrate the First Law of Thermodynamics?
  • The equation $$\delta h = q - w_{shaft}$$ directly exemplifies the First Law of Thermodynamics by highlighting how energy is conserved within a system. It shows that the change in enthalpy ($$\delta h$$) results from the heat added to the system ($$q$$) minus any work done by the system ($$w_{shaft}$$). This encapsulates the idea that energy can change forms but cannot be lost or created, aligning perfectly with the concept of energy conservation.
• Discuss the significance of differentiating between heat transfer and work done when applying the equation $$\delta h = q - w_{shaft}$$ in chemical processes.
  • Differentiating between heat transfer ($$q$$) and work done ($$w_{shaft}$$) is crucial for accurately assessing how energy moves through a chemical system. Heat transfer reflects thermal energy changes due to temperature differences, while work encompasses mechanical energy changes related to volume changes or movement. By understanding both components, engineers can design systems that optimize energy efficiency and control reaction conditions effectively, ensuring desired outcomes.
• Evaluate how applying the equation $$\delta h = q - w_{shaft}$$ could affect process design in chemical engineering.
  • Applying the equation $$\delta h = q - w_{shaft}$$ fundamentally impacts process design by allowing engineers to calculate energy requirements for reactions or separations accurately. By manipulating values of heat transfer and shaft work, engineers can optimize conditions for maximum efficiency, reduce costs, and enhance safety. Furthermore, this equation assists in integrating thermal management strategies within larger systems, ensuring that processes not only meet performance standards but also adhere to sustainability goals by minimizing waste and maximizing energy recovery.

Related terms

Enthalpy:

A thermodynamic quantity that represents the total heat content of a system, often used to measure energy changes during chemical reactions.

First Law of Thermodynamics:

A fundamental principle stating that energy cannot be created or destroyed, only transformed from one form to another, emphasizing the conservation of energy in processes.

Work:

The energy transfer that occurs when a force is applied to move an object over a distance, commonly associated with mechanical or shaft work in thermodynamic systems.