Chemical equilibrium refers to the state of a reversible reaction in which the forward and backward reactions take place at a similar rate. In this state, the concentrations of the reactants and products are stable and do not change with time. In a reversible reaction, reactants (A+B) are constantly converted to products (C+D) and vice versa. This means that the forward reaction and the reverse reaction take place simultaneously.
Read on for some thoughts on why this can be a difficult topic for teachers and students, suggestions for improving the problem, and thoughts on why virtual labs can make things easier.
There are three explanations, in particular, why balance can be problematic for even the most industrious student.
Equilibrium reactions are complex chemical activities that
take place in a closed system that cannot be seen or felt. Since the process can only be represented with little reference to the real world, it will be difficult for students to stay motivated.
Figure 1: Equilibrium constant
The equilibrium constant Kc is a measure of the composition of the reaction at equilibrium. Its value is equal to the reaction coefficient in the equilibrium reaction. The constant is calculated by dividing the products' concentration (or thermodynamic activity) by the concentration of the reactants. The concentration of each species is raised to the power of the coefficient of that species in a balanced chemical equation as shown in the figure
Figure 2: Reaction coefficient
The reaction coefficient Q can be used to predict the direction of a chemical reaction compared to the equilibrium constant Kc. It is calculated similarly to Kc. However, the concentrations of the products and reactants are measured at any time, when the reaction is NOT in equilibrium.
Le Chatelier's Principle
The principle states that when the equilibrium is disturbed by a change in conditions, the equilibrium will shift left or right (towards the reactants or products) to counter this change. So, under different conditions, a new equilibrium is established. Its effect can be felt in:
Exothermic reactions release energy. Accordingly, in this case, heat is regarded as a product. As we add more heat to the system, the equilibrium shifts to the side of the reactants to counteract the increase in products. In an endothermic reaction, heat is considered a reactant because the reaction consumes energy. Therefore, an increase in temperature shifts the equilibrium to the right.
If we increase the pressure, the equilibrium shifts to lower the pressure again. This is achieved by reducing the number of molecules in the system. So if we increase the pressure, the equilibrium will shift to the side where the number of molecules is less.
If we increase the concentration of molecules on one side of the equation, the equilibrium shifts to the opposite side. For example, if we increase the concentration of reactants, the equilibrium shifts to the product side.
With those points in mind, here are a few things you can do in your equilibrium class to make it more fascinating, convenient, and fun for you and your students.
People love stories. One way to build a story revolves around a true story of how a particular scientist struggled to get to the information students were studying. This can increase student interest and provide valuable insight into the nature of research and the human side of diligent scientific discoveries.
In 1803 the concept of chemical equilibrium was born when Bertollet discovered that some chemical reactions are reversible.
He argued that for a chemical reaction to be in equilibrium, the rates of the forward and backward reactions must be the same.
In 1884, the French chemist and engineer Henri-Louis Le Chatellier proposed one of the central concepts of chemical equilibrium. Le Chatelier's principle can be formulated as follows: A change in any of the variables describing a system in equilibrium causes a change in the position of the equilibrium, which opposes the effect of this change. Le Chatelier's principle describes a system's situation when something temporarily unbalances it. This section focuses on three ways we can change the conditions for an equilibrium chemical reaction:
(1) Changing the concentration of one of the reaction components
(2) System pressure change
(3) Change the temperature at which the reaction takes place.
Telling the stories of the scientists behind science is one way to "humanize" this topic. Showing students the real-world application of a topic can stimulate their interest and motivate them by showing them why what they are learning is important.
The catalyst provides an alternative pathway for the reaction with lower activation energy, which allows the reaction to proceed more rapidly. The catalyst does not change the reaction equilibrium; You can only increase the speed. Without a catalyst, the reaction proceeds in the same direction, only slower.
Figure 4: A substrate-to-product reaction is a transition from one energy state to another. There is a transition state between the substrate and the product. This state has a higher energy level than the substrate and product. The catalyst lowers this energy level so that the transition energy is reached more easily, resulting in a faster reaction.
When a topic is as complex and abstract as equilibrium, visualization can make all the difference.
Figure 4: the Haber process reaction chamber setup.
The Haber process was discovered by Fritz Haber and Karl Bosch. It is used in the manufacture of fertilizers by fixing atmospheric nitrogen. The catalyzed reaction converts nitrogen (N2) and hydrogen (H2) into ammonia (NH3) under conditions of high temperature/pressure. Formation of ammonia production. Two gases - nitrogen and hydrogen - flow into the reaction chamber containing the catalyst, where they are converted into ammonia. The reaction products along with the remaining reactants flow into a condenser with a cooling system where the ammonia is liquefied and removed from the system while the leftover nitrogen and hydrogen are put back into the system.
Visualization can be very helpful in understanding the mechanics, but when learning all the chemical names and their sequences for a test, there are few options other than memorization. An example of a memory aid is "ComPleTe" for three ways we can change the conditions for an equilibrium chemical reaction, where small case letters are not considered as shown
C - Concentration
P - Pressure
T - Time
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