Lecture 131: Measuring Reaction Rate: To measure a reaction rate, we usually monitor either a product or a reactant for its change. Any physical characteristic related to the quantity or concentration of a product or reactant can be monitored. Some of the characteristics to be monitored are: change in pressure, change in color (spectroscopic measurement), temperature for exothermic or endothermic reaction, and presence of certain key substance The change can be plotted on a graph, and from the graph, we can get the average rate or the instantaneous rate by either graphical methods or using a computer for the data analysis. Rate Constants and the Orders: Usually, the rate of a reaction is a function of the concentrations of reactants. For example, the rate of the reaction 2NO+O2→2NO2 has the form: Rate=k[O2][NO]2 The rate is proportional to the concentration of O2, usually written as [O2] and is proportional to the square of [NO], or [NO]2. The orders of 1 and 2 for [O2] and [NO]respectively have been determined by experiment, NOT from the chemical equation. The total order of this reaction is 3 (=2+1). Note that orders are NOT determined from the stoichiometry of the reaction equation. Lecture132:
Lecture 131: Measuring Reaction Rate: To measure a reaction rate, we usually monitor either a product or a reactant for its change. Any physical characteristic related to the quantity or concentration of a product or reactant can be monitored. Some of the characteristics to be monitored are: change in pressure, change in color (spectroscopic measurement), temperature for exothermic or endothermic reaction, and presence of certain key substance The change can be plotted on a graph, and from the graph, we can get the average rate or the instantaneous rate by either graphical methods or using a computer for the data analysis. Rate Constants and the Orders: Usually, the rate of a reaction is a function of the concentrations of reactants. For example, the rate of the reaction 2NO+O2→2NO2 has the form: Rate=k[O2][NO]2 The rate is proportional to the concentration of O2, usually written as [O2] and is proportional to the square of [NO], or [NO]2. The orders of 1 and 2 for [O2] and [NO]respectively have been determined by experiment, NOT from the chemical equation. The total order of this reaction is 3 (=2+1). Note that orders are NOT determined from the stoichiometry of the reaction equation. Lecture132:
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