Question

For each reaction, determine the sign of AH, indicate whether the process is exothermic or endothermic, and draw an enthalpy diagram.
a) 2 NO (g) + 3/202(g) -› N20s (s) + 223.7 kJ AH=

b) 2N02(g) + 114.2 kJ + 114.2k] -› 2N0(g) + O2(g) AH=

Answer 1

Answer

(a) Exothermic process, ΔH = -223.7 kJ.

(b) Endothermic process, ΔH = +228.4 kJ

Diagram for exothermic and endothermic processes is shown below:

Explanation

While heat is not really a reactant or a product in a chemical reaction, it is convenient to treat it as such. For an exothermic reaction, heat is released during the reaction and we can consider heat as a product. For an endothermic reaction, the reverse is true and we can consider heat as a reactant.

Let's consider the given reactions:

The reaction/process is exothermic, and ΔH = -223.7 kJ.

The reaction/process is endothermic, and ΔH = (+ 114.2 + 114.2) kJ = +228.4 kJ.

The enthalpy diagram for exothermic and endothermic processes are shown below.