CHMA10H3 Lecture Notes - Lecture 17: Delta Wing, Enthalpy, Exothermic Process
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CHMA10H3 Full Course Notes
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Enthalpy change (delta h): is the heat evolved in a reaction at constant pressure. Enthalpy is one aspect of thermodynamics, which is the study of heat movement in a chemical system. Exothermic: when delta h is negative, heat is being released by the system. Chemical heat packs contain iron filings that are oxidized (lose e-)in an exothermic reaction- your hand get warm because the released heat of the reaction is transferred to your hands. Endothermic: when delta h is positive, heat is being absorbed by the system. Chemical cold packs contain nh4no3 that dissolves in water in an endothermic process- your hands get cold because the pack is absorbing your heat: relationships involving h. Combustion of propane releases heat (delta h= -2044 kj/mol) If we multiply the reaction by a given number (e. g. x2), we also must multiply the value of delta h (delta h= -4088 kj/mol)
