Exothermic reactions enthalpy level diagrams

An exothermic reaction is one in which heat energy is transferred (given out) to the surroundings. The sign of AH for an exothermic reaction is negative. An enthalpy level diagram for an exothermic reactions is ... 

Figure 5.31 Enthalpy level diagram for an exothermic reaction - the combustion of methane... 

Figure 6.12 a General enthalpy level diagram for uncatalysed and catalysed reactions of an exothermic reaction, b The mountain pass analogy for the mechanism of catalytic action stressing the idea of the creation of an alternative reaction pathway... 

Endothermic reactions are reactions in which the specific enthalpy of the products E is greater than the specific enthalpy of the reactants Er E > Er), and the heat of reaction AHr is positive. Endothermic reactions take away heat from the reaction medium and hence require a continuous supply of heat. On the contrary, exothermic reactions are reactions in which Ep < Er and the heat of reaction AHr is negative. Exothermic reactions liberate heat to the reaction medium. The energy level diagram for the exothermic reaction is shown in Figure 2.2. 

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