With regard to the question of heat of reaction, what is heat of reaction

I can't remember a little bit of high school chemistry, but the constant pressure reaction and the constant volume reaction are different, so the constant pressure reaction heat and the constant volume reaction heat are also different.

If the constant pressure reaction does not do external work, the pressure remains unchanged, no matter how it is reflected, he will not do external work.

The constant volume reaction has to do work externally, and the volume of the constant volume reaction becomes larger after the reaction under normal emptying, but the constant volume cannot become larger, so it is compressed, so it has to work externally, and vice versa!

As you said, you just don't know the difference between the system and the environment.

For the same chemical reaction, regardless of constant volume or constant pressure reaction, as long as the amount is the same, the energy released should be the same", which only emphasizes how much heat is objectively released by the reaction, and does not consider whether the heat is absorbed or dissipated by the system.

Whereas, the constant pressure heat of reaction and the constant volume heat of reaction are the results.

For example, if a + b = 2c, the amount of the product is equal to the reactant, then the reaction is naturally constant pressure; But what if the reaction is a+b=c or a+b=3c? The three situations are not the same, so the situations mentioned in the book that you said all exist.

A chemical reaction occurs under isothermal isobaric pressure, and when no other work is done, the thermal effect of the reaction is equal to the amount of change in the enthalpy of the state function of the system.

Internal energy, volume, and enthalpy are state quantities, and only the initial and final states need to be taken into account when calculating. It's all δv, so how can you not count it. I subtract it just because it is not included. You're thinking too complicated

It depends on the energy consumption.

The heat of reaction refers to the heat released or absorbed by the system when the temperature of the product returns to the starting temperature of the reactant after a chemical reaction occurs under constant pressure and without non-expansion work.

In other words, the heat of reaction usually refers to the amount of heat emitted or absorbed by a system during chemical changes in isothermal, isobaric, and state processes. The heat of chemical reaction comes in many forms, such as:

Heat of generation, heat of combustion, heat of neutralization, etc. The heat of chemical reaction is an important thermodynamic data, which is determined experimentally, and the main instrument used is called a "calorimeter".

qv=qp, first u q w, u is the thermodynamic energy of the system, according to the first law of thermodynamics u q w qv p v, i.e., qv u p v.

The book defines that when only the volume work is done and the temperature of the reactant and the product are equal, the heat absorbed or released by the reaction is called the heat of reaction, where the heat of reaction under the condition of constant volume is called the heat of reaction of constant volume, because the volume is unchanged, that is, v 0, so qv u, the heat of reaction of constant volume is equal to the thermodynamic energy change of the system, that is, qv=qp.

The constant volume heat indicates that the volume work w is 0, so the heat absorbed by the closed system from the environment is all used to increase the thermodynamic energy of the system, or the heat released by the closed system from the environment is all due to the decrease of the thermodynamic energy of the system.

Heat of reaction usually refers to the heat of reaction when a chemical reaction occurs without non-expansion work, if the temperature of the product returns to the starting temperature of the reactant, the heat released or absorbed by the system is called the heat of reaction.

There are generally two kinds: isochoric heat of reaction and isobaric heat of reaction. The macroabrasive thermal effect (qv) of the isochoric process reaction is equal to the change in the internal energy of the reaction (δu); The thermal effect (qp) of the reaction in the isobaric process is equal to the enthalpy change (δh) of the reaction

Enthalpy change refers to the increment of enthalpy in which a process takes place in the system.

The isobaric heat of reaction of the system is equal to the enthalpy change.

There are many forms of heat of chemical reaction, such as: heat of formation, heat of combustion, heat of neutralization, etc. The heat of chemical reaction is an important thermodynamic data, which is determined experimentally, and the main instrument used is called a "calorimeter".

Enthalpy changes are the amount of enthalpy changes in the enthalpy of an object. enthalpy is a combination of internal energy and flow work)。

The heat of reaction usually refers to the heat of reaction when a chemical reaction occurs under constant pressure and without non-expansion work, if the temperature of the product returns to the starting temperature of the reactant, then the heat released or absorbed by the system is called the heat of reaction.

In other words, the heat of reaction usually refers to the amount of heat emitted or absorbed by the system when physical or chemical changes occur during isothermal and isobaric processes.

When the chemical reaction occurs under constant pressure and without non-expansion work, if the temperature of the product returns to the starting temperature of the reactant, the heat released or absorbed by the system is called the heat of reaction.

Simply speaking, the heat emitted or absorbed by the system when physical or chemical changes occur in the process of isothermal and isobaric processes.

chemical

reaction

See "Reaction Heat Effects". Referred to as heat of reaction, it is the heat released or absorbed by chemical reactions at isotherm. In principle, the heat of reaction can be determined by two experimental methods:

1) Direct measurement with a calorimeter, for example, the reaction is carried out in a closed vessel, and the heat of reaction can be calculated by energy balance; (2) The reaction equilibrium constant at different temperatures is determined first, and then the thermodynamic formula of correlation reaction heat, reaction equilibrium constant and temperature is used to calculate the heat of reaction. For chemical reactions where it is difficult to control and determine the heat of reaction or equilibrium constant, Gaisce's law proposed by 1840 (the thermal effect of a chemical reaction or physical change is independent of its pathway) can be used. Synthesis from the most stable elementalization at constant temperature using the heat of generation (1

mol of enthalpy of a compound) or heat of combustion (1mol of enthalpy change when a substance is completely combusted) is calculated indirectly.