An overview on Geometric Arrangement of Ions in an Ionic Solid

Chemical equilibrium, state of a reversible chemical reaction in which the proportions of reactants and products remain unchanged. A reversible chemical reaction is one in which the products immediately react to generate the reactants. At equilibrium, the two opposing reactions proceed at the same rate, or velocity, and so there is no net change in the concentrations of the chemicals involved. At this point, the reaction may be regarded as complete; that is, the maximum conversion of reactants to products has occurred for any specified reaction state.

Chemical equilibrium is the state of a chemical process in which both the reactants and the products are present in concentrations that have no further tendency to change with time, and so there is no observable change in the parameters of the system. It occurs when the forward reaction progresses at the same pace as the reverse reaction, and it is known as the steady state. The reaction rates of the forward and backward reactions are not always identical, but they are nearly equal in most cases. There are no net changes in the concentrations of the reactants and products. Dynamic equilibrium is the term used to describe such a condition.

It is possible to demonstrate, using statistical mechanics and chemical thermodynamics approaches, that the equilibrium constant is related to the change in the thermodynamic quantity known as the standard Gibbs free energy that occurs as a result of the chemical reaction. As shown in the equation, the standard Gibbs free energy of the reaction, denoted by G°, is equal to the negative natural logarithm (-log) of the equilibrium constant multiplied by the gas constant (R) and the absolute temperature (T). 

The standard Gibbs free energy of the reaction, denoted by G°, is equal to the difference between the standard free energies of the products and that of the reactants.

Based on the measured or derived values of standard free energy of substances, the equation allows for the computation of the equilibrium constant, or the relative amounts of products and reactants in equilibrium.

Types of Chemical equilibrium:

• Equilibrium of homogeneity-

All reactants and products are in the same phase and are therefore incompatible with separation.

2NH3⟶N2(g) + 3H2(g) 

• Equilibrium in a heterogeneous environment-

The reactants and products do not exist in a homogeneous phase and may thus be separated.

NH4OH ⟶ NH3 (g) + H2O(l)

Chemical equilibrium criteria:

• The reaction must occur in a sealed jar.
• Reversibility is required for the reaction.
• The reactants’ temperature, pressure, and concentration stay unchanged.

Chemical equilibrium law:

Equilibrium concentration is quantified using the term equilibrium constant. While the forward and reverse processes have identical rates at equilibrium, their rate constants are often different. To find the equilibrium constant, consider a simple reversible reaction occurring at constant temperature.

A + B → C + D

According to the law of active mass, the rate of a chemical reaction is proportional to the product of the reactant’s concentration in moles inappropriate power and the temperature and pressure at which it occurs.

A and B convert at a rate proportional to their concentration, represented by r1.

r1 = k1 × [A] × [B]

k1 is a constant referred to as the rate constant or rate coefficient, and square brackets denote the concentrations of the chemicals encompassed in the brackets (mol/liter).

Similarly, the conversion rates of C and D are as follows: 

r2 = k2 × [C] × [D]

Both rate constants will be equal at equilibrium, 

The equilibrium constant at a given temperature is denoted by Keq.

The Equilibrium Constant’s Applications

Equilibrium constants can be tabulated and referred to as needed.

For example, we can determine whether a reaction system will react nearly completely (very big K), virtually completely (very tiny K), or somewhere in between. The greater the value of K, the more inclined the reaction will be to the right (more products). The lower K is, the more the reaction will seek equilibrium to the left (more reactants).

Reaction Quotient-When the system is not in equilibrium or when we are uncertain if the system is in equilibrium, we cannot establish the equilibrium constant using measured activities. The same formalism can still be used to determine a parameter called the reaction quotient, Q. The reaction quotient is a parameter that indicates whether the system is in equilibrium or not. When the system is in equilibrium, our new parameter, Q = K.

CONCLUSION- 

The equilibrium state is one in which the concentrations of reactants and products remain unchanged. Although there appears to be no change in equilibrium, this does not mean that all chemical reactions have ended. When the volume of the system decreases, the equilibrium shifts in favour of the direction that produces less moles of gas. When the volume of the system increases, the equilibrium shifts in favour of the direction that produces the most moles of gas.