In the chemical equation how would you represent the following effects?

CH₄ + 2O₂ → CO₂ + 2H₂O + Heat

Correct option is B

Correct Answer: (b) Exothermic reaction

An exothermic reaction is a chemical reaction that releases heat as a product. In chemical equations, it is typically represented by indicating the release of heat either explicitly or implicitly.

Key Features of Representing Exothermic Reactions:

Release of Heat in the Products:

• The release of heat can be shown by adding the term + Heat or + Δ to the products.

• Example:
  CH4+2O2→CO2+2H2O+Heat

Thermodynamic Representation:

• In thermodynamic terms, the heat release is represented by ΔH<0, where ΔH is the change in enthalpy.

Heat Release in Practical Systems:

• Exothermic reactions often lead to a rise in temperature of the surroundings, indicating energy transfer.

Additional Information:

Endothermic Reactions

An endothermic reaction is a chemical reaction that absorbs energy, usually in the form of heat, from its surroundings. As a result, the temperature of the surrounding environment decreases during the reaction.

Key Features of Endothermic Reactions:

• Energy Absorption:

• Heat energy is taken in to break the bonds of the reactants, which requires more energy than is released during the formation of product bonds.

• ΔH (Enthalpy Change):

• The enthalpy change (ΔH\Delta HΔH) is positive because the system gains energy.

• Temperature Effect:

• The surrounding environment feels cooler because heat is absorbed during the process.

• Non-Spontaneous Nature:

• Many endothermic reactions do not occur spontaneously and may require continuous energy input to proceed.

Examples of Endothermic Reactions:

• Photosynthesis:
  6CO2+6H2O+Light Energy → C6H12O6+6O2

• Plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen.

• Melting of Ice:
  H2O(s)+Heat → H2O(l)

• Heat is absorbed to change ice into liquid water.

• Evaporation of Water:
  H2O(l)+Heat → H2O(g)

• Heat is required to change water from liquid to gaseous form.

• Decomposition of Calcium Carbonate:
  CaCO3(s)+Heat → CaO(s)+CO2(g)

• Heat is absorbed to break calcium carbonate into lime and carbon dioxide.

• Boiling of Liquid:

• Heat is absorbed when liquids like water or ethanol are converted to vapor.