Intramolecular Forces Question 3

The potential energy as a function of internuclear distance for three diatomic molecules, $\ce{X_2}$ , $\ce{Y_2}$ , and $\ce{Z_2}$ , is shown in the graph above. Based on the data in the graph, which of the following correctly identifies the diatomic molecules, $\ce{X_2}$ , $\ce{Y_2}$ , and $\ce{Z_2}$ ?

\begin{array}{c c c c} & \ce{X2} & \ce{Y2} & \ce{Z2} \\ \hline \text{(A)} & \ce{H2} & \ce{N2} & \ce{O2} \\ \text{(B)} & \ce{H2} & \ce{O2} & \ce{N2} \\ \text{(C)} & \ce{N2} & \ce{O2} & \ce{H2} \\ \text{(D)} & \ce{O2} & \ce{H2} & \ce{N2} \\ \end{array}

Approach

Stronger bonds have lower potential energy (they are more stable). In the graph, $\ce{Y2}$ appears to have the lowest potential energy, indicating the strongest bond. Conversely, $\ce{X2}$ has the weakest bond and greatest pontential energy.

Hydrogen molecules involve a single bond, oxygen double, and nirogen triple (which can be found by drawing lewis structures). Triple bonds are stronger than double bonds, which are stronger than single bonds.