Introduction to Chemical Reactions Chemical reactions involve the rearrangement of atoms to form new substances with different properties. These reactions can b...
Chemical reactions involve the rearrangement of atoms to form new substances with different properties. These reactions can be classified based on the energy changes that occur during the process.
Exothermic reactions release energy to the surroundings, resulting in an increase in temperature. Examples include combustion reactions and neutralization reactions. Endothermic reactions absorb energy from the surroundings, leading to a decrease in temperature. Photosynthesis and thermal decomposition are endothermic processes.
Reaction profiles illustrate the energy changes during a chemical reaction. The highest point on the profile represents the activation energy, which is the minimum energy required to initiate the reaction and break existing bonds. After crossing the activation energy barrier, new bonds form, and energy is released (exothermic) or absorbed (endothermic).
Problem: Identify whether the following reaction is exothermic or endothermic based on the given reaction profile:
Solution:
During a chemical reaction, existing bonds must be broken, requiring an input of energy. When new bonds form, energy is released. The overall energy change depends on the difference between the energy required for bond breaking and the energy released during bond formation.
Chemical cells and fuel cells are devices that generate electricity from chemical reactions. In a chemical cell, a redox reaction (involving electron transfer) takes place, generating an electrical current. Fuel cells use hydrogen or other fuels to produce electricity through an electrochemical reaction with oxygen.