Most chemical reactions are reversible, i.e. while reactants form products, the reverse reaction occurs simultaneously with products yielding starting materials. In a closed system it is possible to reach equilibrium, a point at which the rates of formation of products and reactants are equal. Various factors including temperature, volume, and reactant or product concentration, however, affect the degree to which reactions take place. Le Chatelier's principle predicts the effects of changes in these factors on the point at which equilibrium for a reaction is reached. By definition, Le Chatelier's principle states that a change in any outside factor influencing an equilibrium will cause the system to adjust to counteract or minimize the effect of the change. For example, if a solution of a gas in a liquid is heated, according to Le Chatelier's principle, the equilibrium shifts in an attempt to absorb a quantity of the added heat energy.
This module simulates the approach to equilibrium for several reactions. Both the reactant and product concentrations and the equilibrium constant for a reaction can be varied. The program provides numerical and graphic representation of the reactant and product concentrations as a function of the time it takes the reaction of interest to reach equilibrium.
INSTRUCTIONS
1. Select a type of reaction from the Reaction menu.
2. Set the concentrations of the reactants and the products
by adjusting their scroll bars.
3. Enter an Equilibrium constant value into the box (this must
be greater than zero).
4. To view the plot of concentration vs. time and the equilibrium
concentration values, simply click on the Equilibrate button.
5. While viewing the results, you may decide to simulate adding
some reactant or product to the system. To increase the
concentration of one of the reagents, click on the Increase
Concentration menu option. Select reagent A or B when the
menu appears and enter the concentration change you wish to simulate.
6. To return to the reaction set-up screen, click on the Return button.
