1. 1  an implement, such as a hammer, saw, or spade, that is used by hand. 2  a power-driven instrument; machine tool. ( 3 in combination): a toolkit.
The standard enthalpy of combustion is the enthalpy change when one mole of a reactant completely burns in excess oxygen under standard thermodynamic conditions (although experimental values are usually obtained under different conditions and subsequently adjusted).he standard enthalpy of combustion is the enthalpy change when one mole of a reactant completely burns in excess oxygen under standard thermodynamic conditions (although experimental values are usually obtained under different conditions and subsequently adjusted).
Change in enthalpy is sometimes equal to the heat energy that is absorbed or released by the system during a reaction. Enthalpy basically simplifies the calculations when the energy of the system is considered.he Heat energy associated with combustion is called enthalpy of combustion. The reaction is considered only in the presence of oxygen. When one mole of a substance burns completely in the presence of oxygen, then heat change is called enthalpy of combustion.