Final Answer:
The ΔH for the reaction H₂ + 1/2O₂ -> H₂O is -285.8 kJ/mol (Option c).
Step-by-step explanation:
The given value of -285.8 kJ/mol represents the enthalpy change (ΔH) for the reaction H₂ + 1/2O₂ -> H₂O. The negative sign indicates an exothermic reaction, where energy is released to the surroundings. This value is often expressed in kJ/mol to represent the heat evolved or absorbed per mole of reactant (Option c).
The enthalpy change in a chemical reaction is a measure of the heat energy exchanged with the surroundings. In this case, -285.8 kJ/mol signifies that 285.8 kilojoules of energy are released for every mole of H₂ reacting with 1/2 mole of O₂ to produce H₂O. The reaction involves the formation of water, and the negative value indicates a release of energy, making it exothermic.
Understanding the sign and magnitude of ΔH is crucial in assessing the thermodynamic nature of a reaction. In this context, the negative value signifies an exothermic process, and the specific quantity, -285.8 kJ/mol, provides a quantitative measure of the heat released during the formation of water from hydrogen and oxygen.