Provide an example of the enthalpy and entropy of a chemical reaction.

An example of the enthalpy and entropy of a chemical reaction is the combustion of methane.

The combustion of methane (CH4) with oxygen (O2) to form carbon dioxide (CO2) and water (H2O) is an exothermic reaction, meaning it releases heat. The enthalpy change (ΔH) for this reaction is -890.3 kJ/mol, indicating that energy is released during the reaction.

The entropy change (ΔS) for this reaction can be calculated using the formula ΔS = ΣS(products) - ΣS(reactants). The entropy of the products (CO2 and H2O) is greater than that of the reactants (CH4 and O2), meaning that the entropy change is positive. The ΔS for this reaction is 186.3 J/mol*K.

The Gibbs free energy change (ΔG) for this reaction can be calculated using the formula ΔG = ΔH - TΔS, where T is the temperature in Kelvin. At standard conditions (298 K), the ΔG for this reaction is -803.5 kJ/mol, indicating that the reaction is spontaneous and thermodynamically favourable.

Understanding the enthalpy and entropy changes of a reaction is important in predicting whether a reaction will occur spontaneously and how much energy will be released or absorbed during the reaction. The combustion of methane is a common example used in chemistry to illustrate these concepts.