Three systems: Open systems: exchanging matter and energy Closed system: exchanging energy Isolated system: no exchange of matter and energy

The change value of the state properties of the system does not vary depending on the change path.

In a reversible process, the system must achieve thermal balance, mechanical balance (equal internal and external pressures), phase balance, and chemical balance.

Symbol regulations: Q: The system absorbs heat "" releases heat "-" W: The system does work to the outside world "-" The outside world does work to the system " "

Isobaric process: P start = P end = P outside = constant W = -P·△V Isovolumetric process: W=0 Free expansion, vacuum expansion: W=0 (Pout=0) Isothermal reversible expansion of an ideal gas

dU=Cv·dT, dH=Cp·dT Qv=△U (under constant volume conditions) Qp=△H (under isobaric conditions)

At the same time, divide by n to obtain the molar heat capacity at constant pressure and heat capacity at constant volume, and

Isothermal process: △T=0, △U=0, △H=0 The external pressure is constant: W=-Poutside·△V Reversible process: Q=-W

Equal volume process: dV=0 W=0

Isobaric process:

Adiabatic process: Q=0 W=

Response progress:

Calculation of heat of isobaric reaction

The relationship between isobaric reaction heat and isovolumetric reaction heat

The relationship between reaction enthalpy and temperature - Kirchhoff's equation

Only the heat-temperature entropy of a reversible process is equal to the entropy change; the entropy change of an irreversible process is calculated by designing a reversible process.

;>Irreversible, = reversible

Adiabatic system: The irreversible process is a spontaneous process, or a non-spontaneous process in which the environment does work on the system, so dS>0 cannot determine the direction of the reaction. Isolation system: dS≥0

The principle of entropy increase: entropy never decreases

dS isolation = dS system dS ring ≥ 0

Reversible processes are calculated using definitions (physical processes) Entropy is the state function △S=S end-S beginning (chemical reaction)

Entropy change of physical process

entropy change of chemical reaction

A=U-TS Under isothermal conditions, the decrease in A is equal to the maximum work that the closed system can do. G=H-TS Under isothermal and isobaric conditions, the decrease in G is equal to the maximum non-volume work that a closed system can do.

Calculation method: Use the definition Make use of physical meaning Use the relationship between the two The inversion is obtained by using the property that G is a state function and △fG