TABLE OF CONTENTS Heat of chemical reaction = Change in enthalpy of the reaction system at constant pressure. This is a function of the nature of reactants and products involved and also their physical states.
Standard heat of reaction = change of enthalpy when the reaction takes place at 1 atm. in such a manner that it starts and ends with all involved materials at in their normal states of aggregation at a constant temperature of 25 C.
Heat of formation of a chemical compound is the change in enthalpy when elements combine to form the compound which is the only reaction product. Standard heat of formation of a compound , ?H f is the heat of reaction at 25 C and 1 atm.
Standard heat of combustion, ? H c = the enthalpy change resulting from the combustion of a substance in its normal state at 25 C and atmospheric pressure, with the combustion beginning and ending at 25 C. Generally gaseous CO 2 and liquid water are the combustion products.
Standard heat of reaction, ? H R can be calculated from the heats of formation of the reactants and the products by the relation
?H R = ? ?H f ( products ) - ? ?H f ( reac tan ts ) at 25 C, 1 atm.
It can also be calculated from the heats of combustion of the reactants and products by the relation
?H
