Endothermic Reaction

Definition

An endothermic reaction is a type of chemical reaction in which the system absorbs energy from the surroundings in the form of heat. This means that the products of the reaction have a higher energy content than the reactants, and the reaction requires an input of energy to proceed.

5 Must Know Facts For Your Next Test

1. Endothermic reactions have a positive enthalpy change (ΔH > 0), meaning they absorb energy from the surroundings.
2. Endothermic reactions are often associated with the breaking of chemical bonds, which requires an input of energy.
3. Increasing the temperature of the system or adding a catalyst can help overcome the activation energy barrier in an endothermic reaction.
4. Le Châtelier's principle states that when a system at equilibrium is subjected to a change in one of the conditions, the system will shift to counteract the change and reach a new equilibrium.
5. In the context of Le Châtelier's principle, adding heat to an endothermic reaction at equilibrium will shift the equilibrium to the right, producing more products to absorb the additional energy.

Review Questions

• Explain how the energy changes in an endothermic reaction and how it differs from an exothermic reaction.
  • In an endothermic reaction, the system absorbs energy from the surroundings in the form of heat, resulting in a positive enthalpy change (ΔH > 0). This means that the products of the reaction have a higher energy content than the reactants. This is in contrast to an exothermic reaction, where the system releases energy to the surroundings, resulting in a negative enthalpy change (ΔH < 0). The direction of the energy flow is the key difference between endothermic and exothermic reactions.
• Describe how Le Châtelier's principle applies to an endothermic reaction at equilibrium when additional heat is added to the system.
  • According to Le Châtelier's principle, when a system at equilibrium is subjected to a change in one of the conditions, the system will shift to counteract the change and reach a new equilibrium. In the case of an endothermic reaction at equilibrium, adding heat to the system will cause the equilibrium to shift to the right, producing more products. This is because the endothermic reaction absorbs the additional energy, which helps to counteract the increase in temperature and maintain the equilibrium. The shift towards the products helps to offset the increase in energy input and reach a new equilibrium state.
• Analyze the relationship between activation energy and the feasibility of an endothermic reaction, and explain how this relationship can be used to influence the reaction's progress.
  • The activation energy of a chemical reaction is the minimum energy required to start the reaction. For endothermic reactions, the activation energy is typically higher compared to exothermic reactions. This is because endothermic reactions require an input of energy to break chemical bonds and form new ones, which results in a higher energy barrier that must be overcome. By increasing the temperature of the system or adding a catalyst, the activation energy barrier can be lowered, making it more feasible for the endothermic reaction to occur. This relationship between activation energy and the feasibility of an endothermic reaction can be used to influence the progress of the reaction, as manipulating the conditions to reduce the activation energy can help drive the reaction forward and produce the desired products.

Related terms

Exothermic Reaction: An exothermic reaction is the opposite of an endothermic reaction, where the system releases energy to the surroundings in the form of heat.

Enthalpy: Enthalpy is a measure of the total energy of a system, including the energy required to create the system (internal energy) and the work done to make room for it (pressure-volume work).

Activation Energy: Activation energy is the minimum energy required to start a chemical reaction. Endothermic reactions have a higher activation energy compared to exothermic reactions.