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Data may also commonly be presented as a plot of reaction rate (v) vs. time (t). Again, simple algebraic manipulation is required; for example, calorimetric experiments give: v = q / VΔH where q is the instantaneous heat transfer, ΔH is the known enthalpy change of the reaction, and V is the reaction volume. [2]
The apparent unimolecular rate constant k cat is also called turnover number, and denotes the maximum number of enzymatic reactions catalysed per second. The Michaelis–Menten equation [10] describes how the (initial) reaction rate v 0 depends on the position of the substrate-binding equilibrium and the rate constant k 2.
A plot of the negative natural logarithm of the concentration of A in time minus the concentration at equilibrium versus time t gives a straight line with slope k 1 + k −1. By measurement of [A] e and [P] e the values of K and the two reaction rate constants will be known. [32]
As an example, consider the gas-phase reaction NO 2 + CO → NO + CO 2.If this reaction occurred in a single step, its reaction rate (r) would be proportional to the rate of collisions between NO 2 and CO molecules: r = k[NO 2][CO], where k is the reaction rate constant, and square brackets indicate a molar concentration.
The ideal temperature to optimise the yield of the fastest-forming product will be the lowest temperature that will ensure reaction completion in a reasonable amount of time. [14] The ideal temperature for a reaction under thermodynamic control is the lowest temperature at which equilibrium will be reached in a reasonable amount of time. [15]
a thermodynamic equilibrium constant, denoted by , is defined to be the value of the reaction quotient Q t when forward and reverse reactions occur at the same rate. At chemical equilibrium, the chemical composition of the mixture does not change with time, and the Gibbs free energy change for the reaction is zero. If the composition of a ...
For a reversible reaction, the equilibrium constant can be measured at a variety of temperatures. This data can be plotted on a graph with ln K eq on the y-axis and 1 / T on the x axis. The data should have a linear relationship, the equation for which can be found by fitting the data using the linear form of the Van 't Hoff equation
At a certain voltage E e, equilibrium will attain and the forward and backward rates (v f and v b) will be equal. This is represented by the green curve in the above figure. The equilibrium rate constants will be written as k fe and k be, and the equilibrium concentrations will be written c oe and c re.