It is often useful and important to know how long a reaction must proceed to reach a predetermined concentration of some reagent, or what the reactant and product concentrations will be after a predetermined amount of time has elapsed. Relationships between concentration and time are used to obtain this information. Experiments are performed, and subsequently a mathematical equation derived from the experimental data relates time and concentration to calculate a concentration at any time or a time at any concentration.
When the reaction rate is directly proportional to the concentration of a reagent raised to the first power, the reaction is a first-order reaction. Similarly, if the reaction rate is directly proportional to the concentration of a reagent raised to the second power, the reaction is said to be second-order. In both cases, the rate constant, k, is also used in the equations; this value may either be known or calculated.
This module simulates a first- and second-order reaction. A graphical representation of concentration as a function of elapsed time is shown; k is given for both reactions. The concentration/time equation for either the first- or second-order equation is also displayed.
Instructions
1. Select either a first-order reaction or a second-order reaction by clicking on the appropriate option button. A plot of concentration vs. elapsed time is displayed.
2. Click anywhere on the curve to view the calculations for the concentration of reactant.
