Question

What is the enthalpy of the overall chemical equation

Answer 1

Recall that standard enthalpies of formation can be either positive or negative. The enthalpy of formation of carbon dioxide at 298.15K is ΔH f = -393.5 kJ/mol CO 2(g). Write the chemical equation for the formation of CO2

Answer 2

Answer:

The enthalpy of the overall chemical equation is -304.1 kJ

Explanation:

Enthalpy is an additive property. The overall chemical equation can be obtained by summing up all three elementary steps. So enthalpy of overall reaction is summation of enthalpy changes in each steps.

                    $NO(g)+O_{3}(g)\rightarrow NO_{2}(g)+O_{2}(g)$

                    $\frac{3}{2}O_{2}(g)\rightarrow O_{3}(g)$

                    $O(g)\rightarrow \frac{1}{2}O_{2}(g)$

                 ----------------------------------------------------------------------------------------

                     $NO(g)+O(g)\rightarrow NO_{2}(g)$

Enthalpy of overall reaction = $\Delta H_{1}+\Delta H_{2}+\Delta H_{3}$

                                               = (-198.9+142.3-247.5) kJ

                                                = -304.1 kJ