# Question #47aea

Jul 18, 2015

The reaction is exothermic and $q$ is equal to $- \text{114 kJ}$.

#### Explanation:

You know that the balanced chemical equation for your reaction looks like this

$2 N {O}_{\left(g\right)} + {O}_{2 \left(g\right)} \to 2 N {O}_{2 \left(g\right)}$

and that when 2 moles of nitric oxide, $N O$, react with enough oxygen, 114 kJ of energy are evolved.

This means that when the reaction takes place, energy is actually being released.

In other words, the energy needed to break the bonds of the reactants is exceeded by the energy released when the product is formed,

Simply put, the reaction gives off more than it takes in.

This is characteristic of an exothermic process, so your reaction will be exothermic.

As a rule of thumb, the amount of heat lost or gained by a system is represented from that system's point of view.

When heat is being given off, as is the case here, the system is losing heat to the surroundings. In other words, it ends up will less energy than it started with. If that is the case, then the sign of $q$ must be negative.

$q = \textcolor{g r e e n}{- \text{114 kJ}}$