In this case, for the given information, we can compute the rate of disappearance of NO₂ by using the following rate relationship:
Whereas it is multiplied by the the inverse of the stoichiometric coefficient of NO₂ in the reaction that is 2. Moreover, the subscript <em>f</em> is referred to the final condition and the subscript <em>0</em> to the initial condition, thus, we obtain:
Clearly, it turns out negative since the concentration is diminishing due to its consumption.
The term endothermic process describes a process or reaction in which the system absorbs energy from its surroundings; usually, but not always, in the form of heat.