Question

Difference between change in enthalpy and heat of reaction

Answer 1

For gases, the heat of reaction at a specified temperature is defined as the amount of heat that has to be added to the system to bring about the change from an initial state of pure reactants in stoichiometric proportions at the specified temperature and 1 bar pressure to the pure products at the same temperature and 1 bar pressure. This is equal to the standard change in enthalpy of the reaction at the specified temperature. The process for bringing about this change may involve doing work on the surroundings equal to the volume change for products minus reactants times the applied pressure of 1 bar.