Enthalpy question 7?

Question

Since most chemical reactions are conducted in containers open to the atmosphere, why is the heat of chemical reaction generally expressed as the change in enthalpy?

Answer 1

Heat of a chemical reaction is the difference between the enthalpy of reactants and the enthalpies of product. It is the energy change that takes place when a reactants are converted to products. Hence it is expressed as change in enthalpy (the absolute values of enthalpies of reactants or products cannot be calculated)