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3.
The latent heat of reaction is also called latent heat of reaction, which means that due to factors such as the system temperature being too low (the system has not reached the reaction threshold temperature), insufficient solid-liquid contact, or poor heat transfer, etc.
The latent heat of reaction is caused by the temporary suppression of unanticipated or uncontrolled energy release (or temporary suppression of absorption)
The hazard degree of latent heat of reaction is closely related to the quality of reactants, reaction type, reaction environment and operation mode
Fourth, the relationship between temperature and reaction rate
The reaction is accompanied by a change in thermal energy, which in turn directly affects the reaction rate
Van't Hoff summed up an empirical rule based on a large number of experimental data: for every 10°C increase in temperature, the reaction rate increases approximately 2 to 4 times
(1) Arrhenius formula
The relationship between temperature and reaction rate can be expressed by Arrhenius' empirical formula
The effect of temperature on the reaction rate is usually discussed as the rate constant k changes with temperature.
Differential formula: dlnk/dT=E a (RT 2 )
In the formula, E a represents the experimental activation energy, which can be regarded as a constant independent of T; the rate of change of k value with T depends on the value of Ea
lnk=-E a /(RT)+B
In the formula, B represents the integral constant
Definite integral formula: ln(k 2 /k 1 )=Ea/[R(1/T 1 -1/T 2 )]
This formula assumes that the activation energy is independent of temperature, and the activation energy is calculated based on the k value at two different temperatures
Exponential:
k=Aexp[-E a /(RT)]
This formula describes the exponential relationship of rate with temperature.
(2) Reaction type
The relationship between chemical reaction rate and temperature generally has the following five types, as shown in Figure 24-4
Figure 24-4 The relationship between chemical reaction rate and temperature
The first type is shown in Figure 24-4(a), which conforms to the Arrhenius formula.
Among them, the second type is the focus of this section.
