Open system: There is both material and energy exchange between the system and the environment.

Closed system: no exchange of matter, but there is exchange of energy

Isolated system: neither matter nor energy exchange

Features

Classification by nature

The reactants are negative, the products are positive, and the sum of the stoichiometric numbers is 0

For the same reaction, the stoichiometric numbers are related to the way the chemical equation is written.

Definition: ▲n of a substance in the reaction/stoichiometric number and chemistry of the substance It is related to the way the reaction equation is written, and the specific chemical reaction equation must be specified.

Molar reaction: a reaction with a reaction progress of 1 mol

Definition: The energy transferred due to the temperature difference between the system and the environment

The system absorbs heat from the environment, Q>0

The system releases heat from the environment, Q<0

Definition: A general term for other forms of energy transfer between the system and the environment except heat.

The environment does work on the system, W>0

The system does work on the environment, W<0

Classification of work

Definition: Under isothermal conditions, in a closed system, at constant volume and no non-volume work is done. The heat exchanged between the system and the environment during

△U=Qv, that is, all the heat absorbed (released) by the system from the environment is used to increase (reduce) the thermodynamic energy of the system

Measuring Qv: bomb calorimeter

Definition: Under isothermal conditions, in a closed system, at constant pressure and no non-volume work is done. The heat exchanged between the system and the environment during

Define enthalpy H=U Pv, unit J or KJ, which is a state function and has extensive properties

△H=Qp, that is, all the heat absorbed (released) by the system from the environment is used to increase (reduce) the enthalpy of the system

Endothermic reaction △H>0, exothermic reaction △H<0

Reaction without gas participation △H≈△U

For reactions involving gas, △H=△U △nRT, △n=n (product gas)-n (reactant gas)

Definition: The molar enthalpy change of a chemical reaction in the standard state

Thermodynamic standard state: any temperature T, standard Pure gas/liquid under pressure 100Kpa

Standard molar enthalpy of formation

Calculation method: The standard molar enthalpy change of the reaction is equal to the standard molar enthalpy of formation of each substance participating in the reaction at the same temperature × the sum of their stoichiometric numbers

Notice