CHM138H1 Chapter all: Chemical Reactivity and Mechanisms

• School: UTSG
• Department: Chemistry
• Course: CHM136H1
• Professor: all

Document Summary

Electrons achieve lower energy when they occupy a bonding molecular orbital. The change in enthalpy, h, is the exchange of kinetic energy or heat (q) between a system and its surroundings at constant pressure. The bond dissociation energy is the energy required to break a covalent bond homolytically under standard conditions. Homolytic bond cleavage produces radicals (species containing an unpaired electron) while heterolytic bond cleavage produces ions. The heat of a reaction is the total change in energy, accounting for the breaking and forming of bonds. A positive h means the system absorbed energy from the surroundings and the reaction is endothermic; a negative h means the system gave energy to the surroundings and the reaction is exothermic. Energy diagrams illustrate the change in energy as the reaction proceeds. Entropy, s, is the measure of disorder associated with a system. A spontaneous reaction is one where the the total entropy change (system"s + surroundings") is positive.