The Effect of Temperature on Chemical Equilibrium

Oct 13, 2025 by wbrum.org 75 views

Introduction

Chemical equilibrium is a fundamental concept in chemistry that describes the balance between the forward and reverse reactions of a chemical process. In this article, we will explore the concept of chemical equilibrium using the equation $C_2H_4(g) + H_2(g) \Leftrightarrow C_2H_6(g) + 137 \text{ kJ}$ as a case study. We will examine the effect of temperature on the amount of ethane ( $C_2H_6$ ) formed in this reaction.

What is Chemical Equilibrium?

Chemical equilibrium is a state where the rates of the forward and reverse reactions are equal, resulting in no net change in the concentrations of the reactants and products. This state is achieved when the system reaches a balance between the forward and reverse reactions, and the concentrations of the reactants and products remain constant.

The Equation: $C_2H_4(g) + H_2(g) \Leftrightarrow C_2H_6(g) + 137 \text{ kJ}$

The given equation represents the formation of ethane ( $C_2H_6$ ) from ethylene ( $C_2H_4$ ) and hydrogen ( $H_2$ ). The reaction is exothermic, releasing 137 kJ of energy. This energy release is a key factor in determining the equilibrium constant ( $K$ ) of the reaction.

The Effect of Temperature on Chemical Equilibrium

The temperature of a system can significantly affect the equilibrium constant ( $K$ ) of a reaction. In general, an increase in temperature will shift the equilibrium towards the endothermic direction, while a decrease in temperature will shift the equilibrium towards the exothermic direction.

Applying Le Chatelier's Principle

Le Chatelier's principle states that when a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the equilibrium will shift in a direction that tends to counteract the effect of the change. In this case, if the temperature of the system is increased, the equilibrium will shift towards the endothermic direction, which is the reverse reaction.

What Happens to the Amount of Ethane ( $C_2H_6$ ) When the Temperature is Increased?

Based on the analysis above, when the temperature of the system is increased, the equilibrium will shift towards the reverse reaction, which is:

C_2H_6(g) \rightarrow C_2H_4(g) + H_2(g)

As a result, the amount of ethane ( $C_2H_6$ ) will decrease, as it is converted back into ethylene ( $C_2H_4$ ) and hydrogen ( $H_2$ ).

Conclusion

In conclusion, the amount of ethane ( $C_2H_6$ ) formed in the reaction $C_2H_4(g) + H_2(g) \Leftrightarrow C_2H_6(g) + 137 \text{ kJ}$ will decrease when the temperature of the system is increased. This is due to the shift in equilibrium towards the endothermic direction, which is the reverse reaction.

References

Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
Chang, R. (2010). Chemistry: The central science (11th ed.). McGraw-Hill.
Levine, I. N. (2012). Physical chemistry (6th ed.). McGraw-Hill.

Q: What is chemical equilibrium?

A: Chemical equilibrium is a state where the rates of the forward and reverse reactions are equal, resulting in no net change in the concentrations of the reactants and products.

Q: What is the equation $C_2H_4(g) + H_2(g) \Leftrightarrow C_2H_6(g) + 137 \text{ kJ}$ ?

A: The equation represents the formation of ethane ( $C_2H_6$ ) from ethylene ( $C_2H_4$ ) and hydrogen ( $H_2$ ). The reaction is exothermic, releasing 137 kJ of energy.

Q: What happens to the amount of ethane ( $C_2H_6$ ) when the temperature of the system is increased?

A: When the temperature of the system is increased, the equilibrium will shift towards the endothermic direction, which is the reverse reaction. As a result, the amount of ethane ( $C_2H_6$ ) will decrease, as it is converted back into ethylene ( $C_2H_4$ ) and hydrogen ( $H_2$ ).

Q: What is Le Chatelier's principle?

A: Le Chatelier's principle states that when a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the equilibrium will shift in a direction that tends to counteract the effect of the change.

Q: How does Le Chatelier's principle apply to the equation $C_2H_4(g) + H_2(g) \Leftrightarrow C_2H_6(g) + 137 \text{ kJ}$ ?

A: When the temperature of the system is increased, the equilibrium will shift towards the endothermic direction, which is the reverse reaction. This is an example of Le Chatelier's principle in action, where the system adjusts to counteract the change in temperature.

Q: What are some common factors that can affect chemical equilibrium?

A: Some common factors that can affect chemical equilibrium include:

Temperature: Changes in temperature can shift the equilibrium towards the endothermic or exothermic direction.
Concentration: Changes in concentration can shift the equilibrium towards the direction that tends to counteract the change.
Pressure: Changes in pressure can shift the equilibrium towards the direction that tends to counteract the change.

Q: How can I determine the direction of shift in chemical equilibrium?

A: To determine the direction of shift in chemical equilibrium, you can use Le Chatelier's principle. Ask yourself:

What is the change in concentration, temperature, or pressure?
Which direction will the equilibrium shift to counteract the change?

Q: What are some real-world applications of chemical equilibrium?

A: Chemical equilibrium has many real-world applications, including:

Catalysis: Chemical equilibrium is used in catalysis to speed up chemical reactions.
Chemical synthesis: Chemical equilibrium is used in chemical synthesis to produce desired products.
Environmental science: Chemical equilibrium is used in environmental science to understand and predict the behavior of pollutants in the environment.

Q: What are some common mistakes to avoid when working with chemical equilibrium?

A: Some common mistakes to avoid when working with chemical equilibrium include:

Failing to consider the direction of shift in equilibrium.
Failing to account for changes in concentration, temperature, or pressure.
Failing to use Le Chatelier's principle to predict the direction of shift in equilibrium.

Conclusion

Chemical equilibrium is a fundamental concept in chemistry that describes the balance between the forward and reverse reactions of a chemical process. By understanding chemical equilibrium, you can predict the behavior of chemical systems and make informed decisions in a variety of fields, including chemistry, biology, and environmental science.