Relection 2

Using robust details and ample evidence, create a reflection paragraph that describes 4 learning objectives you met while performing this experiment.  View the learning objectives from the lab manual provided and select four to focus your writing on. Make this a well-constructed paragraph by including an introduction and conclusion sentences, avoiding bulleted lists. Challenge yourself to meet a 250-word count goal.

Virtual Lab Manual
Equilibrium
Synopsis
Equilibrium describes the state of a reversible reaction, in which the forward and backward
reactions happen at equal rates. In this state, the concentrations of reactants and products
are stable and do not change over time. Thus, there are no net changes in the concentrations
of the reactant(s) and product(s). Such a state is known as dynamic equilibrium. It is a
particular example of a system in a steady state.
Thermodynamics
In thermodynamics a closed system is in thermodynamic equilibrium when reactions occur at
such rates that the composition of the mixture does not change with time. Reactions do in
fact occur, sometimes vigorously, but to such an extent that changes in composition cannot
be observed.
Help out a famous scientist
In chemistry there are several different types of equilibria: thermodynamic equilibrium,
diffusive equilibrium, thermal equilibrium, and many more. In the Equilibrium Simulation, you
will learn about the general chemical equilibrium and help a famous scientist to prevent a
global famine. You will learn how to influence and predict the directionality of reversible
reactions in the lab.
Will you be able to apply your knowledge to increase the yields of fertilizer for the crops?
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Learning Objectives
At the end of this simulation, you will be able to…
● Predict the directionality of reversible reactions according to Le Chatelier
● Calculate the equilibrium constant and reaction quotient
● Understand the Haber process
Techniques in Lab
None
Theory
Reversible reaction
In reversible reactions, reactants (A+B) are constantly converted into products (C+D) and
vice-versa. This means that the forward and backward reaction take place at the same time.
The reversibility of a reaction is depicted by double arrows in a chemical equation:
Chemical equilibrium
Equilibrium describes the state of a reversible reaction, in which the forward and backward
reaction happen at equal rates. In this state, the concentrations of reactants and products
are stable and do not change over time.
Equilibrium constant
The equilibrium constant Kc is a measure of the composition of a reaction at equilibrium. Its
value is equal to the reaction quotient in a reaction at equilibrium.
The constant is calculated by dividing the concentration (or thermodynamic activities) of
products by the concentration of reactants. The concentration of each species is raised to
the power of that species’ coefficient in the balanced chemical equation.
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Le Chatelier’s principle
The principle states, that if an equilibrium is disturbed by changing the conditions, the
equilibrium moves to the left or right (reactant or product side) to counteract this change.
Thus, a new equilibrium is established under different conditions.
⮚
Effect of temperature
● Exothermic reactions release energy. Therefore, in this case, heat is considered
a product. If we add more heat to the system, the equilibrium will shift to the
reactant side to counteract the increase in product.
●
In endothermic reactions, heat is considered a reactant because the reaction
consumes energy. Thus, increasing the temperature will shift the equilibrium to
the right.
⮚
Effect of pressure
If we increase the pressure, the equilibrium will move in order to reduce the pressure
again. This is achieved by lowering the number of molecules in the system. Hence, if
we increase the pressure, the equilibrium will shift to the side, where the number of
moles is lower.
⮚
Effect of concentration
If we increase the concentration of molecules on one side of the reaction equation,
the equilibrium will shift to the opposite side. E.g if we increase the concentration of
reactant, the equilibrium will shift to the product side.
Reaction quotient
The reaction quotient Q can be used to predict the directionality of a chemical reaction when
compared to the equilibrium constant Kc.
It is calculated similarly to Kc. However, the concentration of products and reactants are
taken at any point in time t while the reaction is NOT in equilibrium.
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Catalysis
Catalysts offer an alternative route for a reaction with a lower activation energy, thereby
making the reaction proceed at a higher rate. Catalysts do not change the equilibrium of a
reaction; they can only increase the rate. Without a catalyst, the reaction would therefore
still proceed in the same direction, just slower.
Figure 1: A reaction from a substrate to a product is a transition from one energy state to
another. A transition state exists between the substrate and product. This state has a higher
energy level than both the substrate and product. A catalyst will lower this energy level, so
that the transition energy is reached more easily, and this results in a faster reaction.
Haber process
The process was invented by Fritz Haber and Carl Bosch. It is used to produce fertilizer by
fixing atmospheric nitrogen. The catalyzed reaction converts nitrogen (N₂) and hydrogen (H₂)
into ammonia (NH₃) under high temperature/pressure conditions.
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