Classify each of the following as exothermic or endothermic:a. CH₄(g) + 2O₂(g) →∆ CO₂(g) + 2H₂O(g) + 802kJ

Verified step by step guidance

1. Identify the type of reaction: The reaction given is a combustion reaction where methane (CH₄) is reacting with oxygen (O₂) to produce carbon dioxide (CO₂) and water (H₂O).
2. Look at the energy term: The reaction releases 802 kJ of energy, which is indicated by the '+ 802 kJ' on the product side of the equation.
3. Understand the energy flow: In chemical reactions, if energy is released to the surroundings, the reaction is exothermic. If energy is absorbed from the surroundings, the reaction is endothermic.
4. Determine the classification: Since the reaction releases energy (802 kJ), it is classified as exothermic.
5. Conclude with the definition: An exothermic reaction is one that releases energy, usually in the form of heat, to the surroundings.

Key Concepts

Exothermic Reactions

Exothermic reactions are chemical processes that release energy, usually in the form of heat, to the surroundings. This energy release occurs because the total energy of the products is lower than that of the reactants. A common example is the combustion of fuels, where energy is released as heat and light.

Endothermic Reactions

Endothermic reactions absorb energy from their surroundings, resulting in a decrease in temperature of the immediate environment. In these reactions, the energy of the products is higher than that of the reactants. Photosynthesis is a classic example, where plants absorb sunlight to convert carbon dioxide and water into glucose.

Enthalpy Change (ΔH)

Enthalpy change (ΔH) is a measure of the heat content of a system during a chemical reaction at constant pressure. A negative ΔH indicates an exothermic reaction, while a positive ΔH signifies an endothermic reaction. In the given reaction, the release of 802 kJ suggests that it is exothermic, as energy is being released to the surroundings.