Search results
Results From The WOW.Com Content Network
Rate equation. In chemistry, the rate equation (also known as the rate law or empirical differential rate equation) is an empirical differential mathematical expression for the reaction rate of a given reaction in terms of concentrations of chemical species and constant parameters (normally rate coefficients and partial orders of reaction) only ...
As useful rules of thumb, a first-order reaction with a rate constant of 10 −4 s −1 will have a half-life (t 1/2) of approximately 2 hours. For a one-step process taking place at room temperature, the corresponding Gibbs free energy of activation (Δ G ‡ ) is approximately 23 kcal/mol.
Chemical kinetics. Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a reaction occurs but in itself tells nothing about its rate.
The Thiele Modulus was developed to describe the relationship between diffusion and reaction rates in porous catalyst pellets with no mass transfer limitations. This value is generally used to measure the effectiveness factor of pellets. The Thiele modulus is represented by different symbols in different texts, but is defined in Hill [2] as hT .
Arrhenius equation. In physical chemistry, the Arrhenius equation is a formula for the temperature dependence of reaction rates. The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist Jacobus Henricus van 't Hoff who had noted in 1884 that the van 't Hoff equation for the temperature dependence of equilibrium ...
In a chemical reaction, the half-life of a species is the time it takes for the concentration of that substance to fall to half of its initial value. In a first-order reaction the half-life of the reactant is ln(2)/λ, where λ (also denoted as k) is the reaction rate constant.
Iron rusting has a low reaction rate. This process is slow. Wood combustion has a high reaction rate. This process is fast. The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. [1]
In chemical kinetics, the overall rate of a reaction is often approximately determined by the slowest step, known as the rate-determining step ( RDS or RD-step [1] or r/d step [2] [3]) or rate-limiting step. For a given reaction mechanism, the prediction of the corresponding rate equation (for comparison with the experimental rate law) is often ...