Order of a reaction (n) is the sum of the exponents of the concentration terms in a rate equation.
Total order of a reaction is
Conditional or formal electrode potential (E°’) is equal to electrode potential (E) when overall concentrations of oxidised and reduced form in all its forms in a solution are equal to one. Conditional electrode potential includes all effects made by reactions that do not take part in the electron exchange, but lead to change of ion power, changes of pH, hydrolysis, complexing, precipitating, etc.
At 298 K (25 °C) and by converting natural (Napierian) logarithms into decimal (common, or Briggian) logarithms, Nernst’s equation for electrode potential can be written as follows:
Electrode of the first kind is a simple metal electrode immersed in a solution containing its own ion (e.g., silver immersed in a silver nitrate solution). The equilibrium potential of this electrode is a function of the concentration (more correctly of activity) of the cation of the electrode metal in the solution (see Nernst’s electrode potential equation).
Hesse’s law says that reaction heat of some chemical change does not depend on the way in which the reaction is conducted, but only on starting and ending system state. Hesse’s law is also known as the law of constant heat summation. Hesse’s law is also known as the law of constant heat summation. The law was first put forward in 1840 by the Swiss-born Russian chemist Germain Henri Hess (1802-1850).
Hesse’s law can be used to obtain thermodynamic data that cannot be measured directly. For example, it is very difficult to control the oxidation of graphite to give pure CO. However, enthalpy for the oxidation of graphite to CO2 can easily be measured. So can the enthalpy of oxidation of CO to CO2. The application of Hess’s law enables us to estimate the enthalpy of formation of CO.
C(s) + O2(g) →← CO2(g) | ΔrH1 = -393 kJ mol-1 |
CO(g) + 1/2O2(g) →← CO2(g) | ΔrH2 = -283 kJ mol-1 |
C(s) + 1/2O2(g) →← CO(g) | ΔrH3 = -110 kJ mol-1 |
The equation shows the standard enthalpy of formation of CO to be -110 kJ/mol.
The equilibrium constant (K) was originally introduced in 1863 by Norwegian chemists C.M. Guldberg and P. Waage using the law of mass action. For a reversible chemical reaction represented by the equation
chemical equilibrium occurs when the rate of the forward reaction equals the rate of the back reaction, so that the concentrations of products and reactants reach steady-state values.
The equilibrium constant is the ratio of chemical activities of the species A, B, C, and D at equilibrium.
To a certain approximation, the activities can be replaced by concentrations.
For gas reactions, partial pressures are used rather than concentrations
The units of Kp and Kc depend on the numbers of molecules appearing in the stoichiometric equation (a, b, c, and d).
The value equilibrium constant depends on the temperature. If the forward reaction is exothermic, the equilibrium constant decreases as the temperature rises. The equilibrium constant shows the position of equilibrium. A low value of K indicates that [C] and [D] are small compared to [A] and [B]; i.e. that the back reaction predominates.
The equilibrium constant is related to ΔrG°, the standard Gibbs free energy change in the reaction, by
The generalized ideal gas law is derived from a combination of the laws of Boyle and Charles. Ideal gas law is the equation of state
which defines an ideal gas, where p is pressure, V molar volume, T temperature, and R the molar gas constant (8.314 JK-1mol-1).
Mass (m) is the quantity of matter contained in a particle or body regardless of its location in the universe. Mass is constant, whereas weight is affected by the distance of a body from the centre of the Earth (or of other planet). The SI unit is kilogram.
According to the Einstein equation
all forms of energy possess a mass equivalent.
In the special theory of relativity Einstein demonstrated that neither mass nor energy were conserved separately, but that they could be traded one for the other and only the total "mass-energy" was conserved. The relationship between the mass and the energy is contained in what is probably the most famous equation in science,
Where m is the mass of the object and c is the velocity of light. Cockcroft and Walton (1932) are routinely credited with the first experimental verification of mass-energy equivalence.
Onsager relations are an important set of equations in the thermodynamics of irreversible processes. They express the symmetry between the transport coefficients describing reciprocal processes in systems with a linear dependence of flux (Ji) on driving forces (Xj).
In Onsager’s theory the coupling coefficients are equal, Lij = Lji. This is known as reciprocal relations. The theory was developed by the Norwegian chemist Lars Onsager (1903-1976) in 1931.
Reversible reaction is a chemical reaction that can proceed in both the forward and backward directions. When reversible reactions reach equilibrium the forward and reverse reactions are still happening but at the same rate, so the concentrations of reactants and products do not change. A reversible reaction is denoted by a double arrow pointing both directions in a chemical equation.
Generalic, Eni. "Ilkovic equation." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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