System and environment

nature of system

state

Reversible expansion: W=-nRTln (V end/V start)

Thermodynamic energy U (internal energy)

Heat and work (neither are state functions)

enthalpy

Isobaric heat and enthalpy: Qp=ΔU pΔV=ΔH, H=U+pV, state, wide state

Isovolumetric heat: ΔU=Qv

Qp=Qv（Δn）RT

pɵ: pressure=1×10^5Pa

The subscript "r" represents a general chemical reaction, and the superscript "ɵ" represents the standard state. ΔH also has the heat of fusion fus, the heat of solidification sol; the heat of vaporization vap, the heat of condensation coa; the heat of sublimation sub

"m" means that 1 mol of reaction has occurred, and the reaction progress is 1 mol.

Commonly used standard enthalpy change at 298.15K

"f" means "standard generation", not an absolute value, but a relative value relative to the reference state element that generates it.

The aggregation state and even crystal type of the substance should be indicated. (g),(l),(s),(aq),(cr),C(diamond)orC(graphite)

ΔrHɵ(298.15K), unit kJ/mol

stoichiometry

The enthalpy change when 1 mol of a substance is generated from the most stable element is called the molar enthalpy of formation. The enthalpy of formation under the standard state is the standard molar enthalpy of formation (standard molar heat of formation) ΔrHmɵ=∑ΔfHmɵ(product)-∑Δ fHmɵ(reactant) Measurement coefficient

ΔrHmɵ=∑[ΔfHmɵ(298.15K)] product-∑[ΔfHmɵ(298.15K)] reactant=∑ʋB ΔfHmɵ(B,298.15K)

The direction is single. If you want to reverse it, you must use external force to do work on it.

Have the ability to do work. The ability to do work is the internal driving force of spontaneous processes.

There is a certain limit. In short, the spontaneous process always tends to the equilibrium state in one direction. This is the limit of the spontaneous process under this condition.

The degree of chaos refers to the degree of irregularity or disorder of the particles that make up the system. Entropy is a measure of the degree of disorder of the system, represented by the symbol S. It is a state function with extensive properties. The entropy of a certain amount of pure material is a function of temperature and pressure.

Influencing factors

Entropy change and the direction of chemical reactions

The third law of thermodynamics states that at absolute zero, the entropy value of any perfect crystal of pure substance is zero, recorded as S0=0 Entropy change ΔS=S(T)-S0 Note (?): For ions in aqueous solution, the standard molar entropy of H aqueous solution with activity 1 is zero.

The specified entropy of 1 mol of a substance in the standard state is called standard molar entropy, symbol Smɵ (T), and the unit J/mol/K standard entropy is all positive (with exceptions for aqueous solutions) (?). The standard molar entropy of a stable element is not is zero

Calculation of entropy change

Under standard conditions: ΔrGmɵ=∑[ΔfGmɵ(298.15K)] product-∑[ΔfGmɵ(298.15K)] reactant

Gibbs-Helmholtz formula: ΔG(T)＝ΔH(T)-TΔS(T) Commonly used units are ΔrGmɵ(T)=ΔrHmɵ(298.15K)-TΔrSmɵ(298.15K).

Under non-standard conditions, ΔrGm = ΔrGmɵ RTlnJ. This formula is called the isothermal equation of a chemical reaction. The expression of J is similar to concentration entropy (?). For solutions, we use universal concentration, and for gases, we use pressure. Regulations: standard concentration = 1mol/L, standard pressure = 100kPa

standard state in biochemistry

The standard Gibbs function of reactions occurring in living organisms becomes >0 but occurs spontaneously

Coupling reactions in organisms

Reversible reaction: A two-way reaction such as the ammonia synthesis reaction that can proceed in one direction or the opposite direction. Reversibility is a universal characteristic of chemical reactions.

Chemical equilibrium: V positive = V negative, the concentration or partial pressure of the reactants and products in the system remains unchanged, and the equilibrium state is the maximum extent that a chemical reaction can proceed under certain conditions.

Experimental equilibrium constant (referred to as equilibrium constant)

standard equilibrium constant

multiple balances

ΔrGm=ΔrGmɵ RTlnJ, the original formula is equal to 0 at equilibrium, and then through the relationship between J and K, lgKɵ=-ΔrGmɵ/2.303RT, ΔrGm=-RTln (Kɵ/J)

Determine the limit of reaction progress, predict the direction of reaction, and calculate the composition of the equilibrium system

The effect of concentration on equilibrium movement, that is, the change relationship can be deduced through the relationship between Kɵ and ΔrGmɵ

The effect of temperature on chemical equilibrium, lgK1ɵ/K2ɵ=ΔrGmɵ*(1/T1-1/T2)/2.303R. It can be seen that the greater the absolute value of the standard molar enthalpy change, the greater the impact of temperature on the equilibrium constant.

The influence of pressure on balance. If the volume of the system changes from V to V/x, then J=x^(e g)-(a b)Kɵ can be calculated, and then the relationship between equilibrium movement and Δn can be derived.