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).
The enthalpy of reaction measures the heat released/absorbed by a reaction that occurs at constant pressure. Review enthalpy of reaction. 1  At constant volume, the heat of reaction is equal to the change in the internal energy of the system.  At constant pressure, the heat of reaction is equal to the enthalpy change of the system.