We owe our existence to the equilibrium phenomenon occurring in the atmosphere. We breathe in oxygen and exhale carbon dioxide, while plants take in CO2 and release oxygen.This natural process is responsible for the presence of life on Earth. Lots of environmental systems depend for their existence on the fragile equilibrium phenomenon.
For example, the concentration of gases in lake water is managed by the principles of equilibrium. The lives of water plants and animals are indirectly related to the concentration of dissolved oxygen in the water.
For a better understanding of Chemical Equilibrium, the understanding of the following concepts is necessary. So, we start our topic with reversible and irreversible reactions.
In a chain reaction, the substances that combine are called reactants and the new substances formed are called products. For example, when H2 and O2 (reactants) combine they form water H2O (product).
Irreversible reactions
The majority of the reactions, in which the products do not recombine to form reactants, are called irreversible reactions.
They are expected to complete and are represented by putting a single arrow (→) in between the reactants and products.
Reversible reactions
The reactions in which the products can recombine to form reactants are called reversible reactions.
These reactions never go to completion. They are represented by a double arrow (⇆) in between reactants and products. These reactions continue in both ways, i.e., they
consist of two reactions; forward and reverse. So, a reversible reaction is one which can be made to continue in either direction depending upon the conditions.
Forward Reaction
Let us go over a reaction between hydrogen and iodine. Due to the fact that one of the reactants, iodine is purple, while the item hydrogen iodide is colourless, proceedings of the reaction are easily observable. On heating, hydrogen and iodine, vapours in a closed flask, hydrogen iodide are formed. As a result, the purple colour of iodine fades as it reacts to form colourless hydrogen iodide. This reaction is called a forward reaction.
Reverse Reaction
When hydrogen iodide is heated in a closed flask, purple colour appears because of the formation of iodine vapours. In this case, hydrogen iodide functions as a reactant and produces hydrogen and iodine vapours. This reaction is reverse of the above. Therefore, it is called a reverse reaction.
When both of these responses are written together as a reversible response, they are represented as:
Chemical Equilibrium and Dynamic Equilibrium
Equilibrium is a state of rest or balance due to the equal action of opposing forces. However, the balance might be achieved in a variety of methods.
Definition
When the rate of the forward reaction is the same as the rate of the reverse reaction, the structure of the reaction mix stays continuous, it is called a chemical equilibrium state.
Possibilities at Equilibrium
- When reaction stops to continue, it is called static equilibrium. This occurs mainly in the physical phenomenon. For example, a building remains standing rather than falling down because all the forces acting upon it are balanced. This is an example of static equilibrium.
- When a reaction does not stop, just the rates of forward and reverse reactions become equal to each other however occur in opposite directions. This is called dynamic equilibrium state. Dynamic implies reaction is still continuing. At dynamic equilibrium state:
Rate of forward reaction = Rate of reverse reaction
Dynamic Equilibrium
Dynamic equilibrium only takes place in reversible reactions, and it is when the rate of the forward reaction becomes equal to the rate of the reverse reaction. These are dynamic since the forward and reverse reactions are still happening, but the two rates are equal and changeless, so they’re likewise at balance.
Dynamic balance is an example of a system in a stable state. This implies the variables in the equation are constant in time (since the rates of reactions are equivalent). If you take a look at a reaction in dynamic equilibrium, it will look like absolutely nothing is occurring given that the concentrations of each compound stay consistent. However, reactions are in fact continuously taking place.
For example, in case of reaction between hydrogen and iodine vapours, a few of the molecules react with each other to form hydrogen iodide.
At the same time, a few of the hydrogen iodide molecules disintegrate back to hydrogen and iodine.
In the beginning, as the concentration of the reactants is higher than that of the products, the rate of the forward reaction is quicker than the reverse reaction. As the reaction proceeds, the concentration of reactants will gradually reduce while that of products will increase, as a result, the rate of the forward reaction will go on reducing and the reverse reaction will go on increasing and eventually the two rates will end up being equal to each other.
Therefore, the balance will set up and the concentration of different types (H2, I2, HI) ends up being consistent. It is represented as
Macroscopic characteristics of dynamic equilibrium
A couple of essential characteristic functions of dynamic equilibrium are provided below:
- An equilibrium is achievable only in a closed system (in which substances can neither leave nor enter).
- At equilibrium state, a reaction does not stop. Forward and reverse reactions keep occurring at the very same rate but in opposite directions.
- At equilibrium state, the amount (concentration) of reactants and products do not alter. Even physical properties like colour, density, etc. stay the same.
- An equilibrium state is obtainable from, in either case, i.e. starting from reactants or from products.
- Aequilibriumstate can be disturbed and again achieved under the provided conditions of concentration, pressure and temperature.
Take 15 MCQs test
- Question 1: What is responsible for the presence of life on Earth, as mentioned in the introduction?
- A) Irreversible reactions
- B) Dynamic equilibrium
- C) Chemical equilibrium
- D) Reversible reactions
- Answer 1: C) Chemical equilibrium
- Question 2: What type of reactions are represented by a single arrow (→) and do not recombine to form reactants?
- A) Dynamic equilibrium
- B) Irreversible reactions
- C) Reversible reactions
- D) Forward reactions
- Answer 2: B) Irreversible reactions
- Question 3: In a reversible reaction, how are the reactants and products represented?
- A) →
- B) ⇆
- C) ←
- D) ⇄
- Answer 3: B) ⇆
- Question 4: What occurs in a forward reaction?
- A) Formation of reactants from products
- B) Equal rates of forward and reverse reactions
- C) Decrease in concentration of reactants
- D) Formation of products from reactants
- Answer 4: D) Formation of products from reactants
- Question 5: What happens in a dynamic equilibrium state?
- A) Reaction stops completely
- B) Rates of forward and reverse reactions are equal
- C) Concentrations of reactants and products change continuously
- D) Only forward reaction occurs
- Answer 5: B) Rates of forward and reverse reactions are equal
- Question 6: In dynamic equilibrium, what remains constant over time?
- A) Concentrations of reactants and products
- B) Temperature
- C) Rates of forward and reverse reactions
- D) Physical properties like color and density
- Answer 6: A) Concentrations of reactants and products
- Question 7: What is required for equilibrium to be achievable?
- A) Open system
- B) High temperature
- C) Closed system
- D) Low pressure
- Answer 7: C) Closed system
- Question 8: What is the macroscopic characteristic of dynamic equilibrium regarding physical properties?
- A) Physical properties change continuously
- B) Color and density remain constant
- C) High volatility
- D) Variable concentration
- Answer 8: B) Color and density remain constant
- Question 9: What term is used to describe a system in a stable state where variables remain constant over time?
- A) Dynamic equilibrium
- B) Irreversible reaction
- C) Static equilibrium
- D) Unstable state
- Answer 9: A) Dynamic equilibrium
- Question 10: In which direction do reactions occur in dynamic equilibrium?
- A) Only in the forward direction
- B) Only in the reverse direction
- C) Both forward and reverse directions
- D) No reactions occur
- Answer 10: C) Both forward and reverse directions
- Question 11: What happens to the rate of the forward reaction as a reversible reaction proceeds?
- A) It increases
- B) It decreases
- C) It remains constant
- D) It becomes unpredictable
- Answer 11: B) It decreases
- Question 12: What is the main factor that disturbs an equilibrium state?
- A) Concentration, pressure, and temperature
- B) Closed system
- C) Irreversible reactions
- D) Static equilibrium
- Answer 12: A) Concentration, pressure, and temperature
- Question 13: What does a closed system mean in the context of equilibrium?
- A) Substances can leave but not enter
- B) Substances can enter but not leave
- C) Substances can both leave and enter
- D) Substances cannot leave or enter
- Answer 13: D) Substances cannot leave or enter
- Question 14: What is the result of a reaction at static equilibrium?
- A) The reaction stops completely
- B) Equal rates of forward and reverse reactions
- C) Constant change in concentrations
- D) Dynamic equilibrium
- Answer 14: A) The reaction stops completely
- Question 15: What is an example of a system in a stable state with variables constant in time?
- A) Unstable equilibrium
- B) Dynamic equilibrium
- C) Equilibrium with changes
- D) Static equilibrium
- Answer 15: B) Dynamic equilibrium
FAQs (Frequently Asked Questions)
- Q: What is the fundamental process responsible for life on Earth, as mentioned in the tutorial?
- A: The equilibrium phenomenon occurring in the atmosphere, where we breathe in oxygen and exhale carbon dioxide, while plants take in CO2 and release oxygen.
- Q: What are irreversible reactions, and how are they represented?
- A: Irreversible reactions are those where products do not recombine to form reactants. They are represented by a single arrow (→) between the reactants and products.
- Q: How are reversible reactions different from irreversible reactions?
- A: Reversible reactions allow products to recombine with reactants. They are represented by a double arrow (⇆) between reactants and products.
- Q: What is a forward reaction, and can you provide an example?
- A: A forward reaction is the formation of products from reactants. An example is the reaction between hydrogen and iodine, resulting in hydrogen iodide.
- Q: Explain the concept of dynamic equilibrium.
- A: Dynamic equilibrium occurs when the rates of the forward and reverse reactions become equal, allowing the reaction to continue, but with no net change in concentrations.
- Q: How is dynamic equilibrium different from static equilibrium?
- A: In dynamic equilibrium, the reaction continues, but the rates of forward and reverse reactions are equal. In static equilibrium, the reaction stops, and forces are balanced, as seen in physical phenomena like a standing building.
- Q: What macroscopic characteristics define dynamic equilibrium?
- A: Characteristics include achieving equilibrium in a closed system, continuous reactions at equal rates, constant amounts (concentrations) of reactants and products, and the ability to disturb and reestablish equilibrium under specific conditions.
- Q: Can you provide an example of a system in dynamic equilibrium mentioned in the tutorial?
- A: The reaction between hydrogen and iodine vapors, forming hydrogen iodide, illustrates dynamic equilibrium, where molecules both react to form the product and disintegrate back to reactants.
- Q: What factors are necessary for equilibrium to be achievable?
- A: Equilibrium is achievable in a closed system, where substances cannot leave or enter. The conditions of concentration, pressure, and temperature play a crucial role.
- Q: How does concentration change during the progression of a reversible reaction towards equilibrium?
- A: Initially, the concentration of reactants is higher, leading to a faster forward reaction. As the reaction proceeds, the concentration of reactants decreases, and that of products increases until the rates of both reactions become equal at equilibrium.
- Q: Can equilibrium be disturbed, and if so, how can it be reestablished?
- A: Yes, equilibrium can be disturbed. By altering conditions like concentration, pressure, and temperature, equilibrium can be reestablished.
- Q: What is the significance of physical properties in dynamic equilibrium?
- A: Physical properties such as color and density remain constant during dynamic equilibrium, reflecting the stability of the system.
Summary
The tutorial explores the crucial concepts of equilibrium phenomena, emphasizing its role in sustaining life on Earth through the exchange of gases between humans and plants. The intricate balance in environmental systems, such as the concentration of gases in lake water, demonstrates the dependence on equilibrium.To comprehend chemical equilibrium, the tutorial introduces reversible and irreversible reactions, defining reactants and products. The distinction between irreversible reactions, represented by a single arrow, and reversible reactions, denoted by a double arrow, sets the stage for a deeper exploration.
The tutorial delves into the dynamics of forward and reverse reactions, illustrating a reaction between hydrogen and iodine. The observable color changes during these reactions exemplify the concepts of forward and reverse reactions, leading to the introduction of chemical equilibrium.
Chemical equilibrium is defined as a state where the rate of the forward reaction equals the rate of the reverse reaction, resulting in a continuous and balanced reaction mixture. Static equilibrium, where reactions cease, and dynamic equilibrium, characterized by equal and opposite rates of forward and reverse reactions, are explored.
The macroscopic characteristics of dynamic equilibrium are outlined, highlighting its occurrence in closed systems and the constancy of reactant and product concentrations and physical properties.
In a dynamic equilibrium scenario involving hydrogen and iodine vapors, the tutorial illustrates the continuous but balanced reactions, culminating in the establishment of equilibrium and consistent concentrations of involved substances.
The tutorial concludes by emphasizing the disturbance and re-establishment of equilibrium under specific conditions of concentration, pressure, and temperature, providing a comprehensive understanding of the delicate balance governing chemical systems.