Signs of Chemical Equilibrium A sign of the equilibrium of a chemical reaction

Keywords of chemical equilibrium state markers: concentration, invariance, forward and reverse reaction speed, equality judgment to reach the equilibrium state, is a difficult problem for many students. Mainly because it is too theoretical, the author has found a little law after years of research, which is only for the reference of colleagues.

First, let's start with the definition of the equilibrium state, which emphasizes two aspects: the percentage content of each component remains constant; The rate of positive reaction is equal to the rate of reverse reaction. So we also look at it from two sides:

For example, if the reaction a2(g)+b2(g) 2ab(g) is said to be unchanged, it refers to the content, or a description that can indicate the content. The volume fraction of A2, B2 and AB, the quantity fraction of the substance, the mass fraction and the ratio of the number of molecules remain unchanged, the conversion rate of A2 and B2 remains unchanged, the temperature of the system remains unchanged, and the color of the system remains unchanged. For reactions with volume changes before and after the reaction, the average relative molecular weight, pressure, amount of total substance, density, etc. of the system can also be unchanged. If we say equal, we mean that the rate of forward and reverse reactions is equal.

For example, the rate at which AB is generated is equal to the rate at which AB decomposes; The number of molecules that A2 reacts with is equal to the number of molecules that produce A2 per unit of time. Some narratives are certainly not true, such as:

The rate at which B2 is generated is the same as the rate at which B2 is reacted; The rate at which A2 is reacted is equal to that of B2; The concentration of A2 is equal to that of B2; The volume fraction of B2 is equal to that of AB; The conversion rate of A2 is equal to that of B2. You should note that in equilibrium, the rate of positive reaction of the same species is equal to the rate of reverse reaction.

Essence: Positive reaction speed = reverse reaction speed.

1. When the isothermal isochoric changes in the middle air pressure before and after, if the air pressure does not change, the equilibrium is proved. 2. There is a reaction of colored gases, and if the color of the whole system does not change, it reflects the equilibrium. 3. The reaction is accompanied by the transfer of heat, if the system does not transfer heat with the outside world, or keeps the temperature unchanged, it means that the equilibrium is balanced.

First of all, it is necessary to clarify whether ABCD is a solid or not, because solids do not consider the chemical equilibrium rate, and from this aspect alone, V positive does not necessarily mean V inverse.

Furthermore, the gas state or, stably the solution state.

, the ratio of the velocity is equal to the ratio of the stoichiometric number.

It should be that the positive reaction rate is equal to the reverse reaction rate.

But in this question of yours.

The rate of forward and reverse reactions should meet the ratio of the metrological numbers in the chemical equation.

va:vb: is the positive reaction rate.

VC: VD is the reverse reaction rate.

Namely. The balance logo is:

pva=mvc or qva=mvd or pvb=nvc or qvb=nvd the book I just read this morning. Hey hey).

The signs of reaching equilibrium in the chemical reaction 1, v positive = v inverse 2, the quantity and mass of the substance, the quantity and concentration of the substance, the percentage content of the components (volume fraction, mass fraction), and the constant conversion rate of the components can all be used as indicators of reaching equilibrium. 3. The constant total pressure must be aimed at the reaction of the change of gas volume under constant volume and constant temperature, such as N2+3H2 2NH3, because the larger the amount of gaseous substance, the greater the pressure p, then regardless of whether each component is a gas, only the amount of gaseous substance needs to be considered whether the amount of gaseous substance changes, as long as the amount of gaseous substance changes, when the total pressure is constant, the reversible reaction reaches equilibrium. However, for the reversible reaction that does not change before and after the reaction of the volume of the gas, because the amount of the substance of the gas is unchanged in equilibrium or not, p will not change at constant volume and temperature.

Therefore, a constant total pressure cannot be used as a sign to determine equilibrium. For example, the density of the H2+I2 gas mixture is constant when the components are gases before and after the reaction

It is always a constant value and cannot be used as a balance mark; Constant pressure: the amount of reaction of other substances, always a constant value, can not be used as a balance mark, such as: H2 + I2 2Hi.

When the quantitative reaction of unequal substances is a certain value, it can be used as an equilibrium marker 5, and the average relative molecular mass of the mixed gas (m) is constant If each substance is a gas, the quantitative reaction of non-equal substances, such as 2SO2+O2 2SO3, m must be used as an equilibrium marker. For the quantitative reaction of equal substances, such as H2+ BR2 2HBR, M must not be used as an equilibrium marker. If there is non-gas participation, regardless of the amount of equal matter or the amount of non-equal matter, such as c(s) + O2 (g) co2 (g), co2 (g) + c(s) 2co(g), m must mark the equilibrium.

6. The color of the mixed gas must be a reversible reaction with the participation of colored gases, and when the color of the mixed gas remains unchanged, it can be used as a sign of reaching equilibrium. Such as H2+I2 2Hi and 2NO2+O2 N2O47, when the temperature does not change with time. For insulated systems, equilibrium is marked when the temperature in the system is constant.