TERMOQUIMICA Teoría 6 - Transferencia de calor a volumen constante Qv

Thermodynamics and Constant Volume Reactions

Introduction to the First Principle of Thermodynamics

• The first principle of thermodynamics is applied specifically to reactions occurring at constant volume, particularly those involving solids and liquids without gas release.

• Reactions in closed containers, such as pressure cookers or autoclaves, exemplify processes where volume remains unchanged despite potential gas production.

Examples of Constant Volume Reactions

• Cooking in a pressure cooker is highlighted as an example where the system's volume does not change, allowing for specific thermodynamic considerations.

• Other examples include sterilization processes in laboratories and wine fermentation, both occurring in sealed environments that maintain constant volume.

Mathematical Adaptation of the First Principle

• The general equation for the first principle states that the change in internal energy (ΔU) equals heat (Q) plus work (W). This will be adapted for constant volume scenarios.

• In this context, work is defined as negative pressure times the change in volume (W = -PΔV), which leads to simplifications when ΔV equals zero.

Implications of Constant Volume on Energy Changes

• Since ΔV is zero during constant volume reactions, both work and changes in internal energy simplify significantly. Thus, ΔU becomes equal to Q transferred during the reaction.