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).
â¢ ïG = ïH-TïS (ïG in units of kJ/mol) ïµ ïH is enthalpy (kJ/mol), T is temperature (K), ïS is change in entropy (J/molÂ·K) â¢ In any spontaneous process (constant T and P), the free energy of the system always decreases! Spontaneity is determined by both the enthalpy and entropy of a reaction. Enthalpy, Entropy and Spontaneity Nature tends toward state of lower energy. ï· Many spontaneous processes are exothermic (e.g. combustion reactions have ï ï Nature tends to become more disordered or random.