Experiment 10
Chemistry 106
74
Summary:
We added reactant. When equilibrium is re-established, there is more product and less reactant. We say the position of equilibrium has been shifted to the right. If we add product, we would observe the opposite. There would be more reactant and less product or in other words, the equilibrium position shifted to the left.
These observations can be summed up by Le Châtelier's Principle: A system at equilibrium will respond to an external stress by adjusting itself to relieve the stress. Le Châtelier's principle is commonly observed in chemical reactions.
In this experiment we will use two different methods to disturb systems at chemical equilibrium.
1. Change the concentration of one or more species involved in the reaction
2. Change the temperature
How a system responds to a change in temperature depends on whether the reaction is exothermic or endothermic. If a reaction is exothermic, we consider heat as a product. Increasing the temperature means to add product. The equilibrium position will shift to the left to consume the added heat. If a reaction is endothermic, we would consider heat as a reactant. Increasing the temperature means we are adding reactant. The equilibrium position will shift to the right.
In this experiment, you will apply Le Châtelier's Principle on four different reactions. For each experiment state the stress (too much heat, too much \( \mathrm{Cl}^{-} \), etc.) and the response (e.g. equilibrium position shifts to the left to consume excess \( \mathrm{Cl}^{-} \), more \( \mathrm{HCl} \) is formed)
