Where is potential energy seen in chemistry?

1 Answer
Jun 1, 2016

The potential energy of a chemical bond is where one might see potential energy.

http://www.mhhe.com/

On the yy axis, we have the potential energy in "kJ/mol"kJ/mol, and on the xx axis, we have the distance rr between the left atom ("H"H) and the right atom ("H"H)'s nuclei.

  • As the two hydrogen atoms move closer together, the attraction between hydrogen A's valence electron and hydrogen B's proton increases. Same with hydrogen A's proton and hydrogen A's valence electron.

  • An energy of attraction is conventionally negative, so we move downwards on the potential energy curve.

If we move leftwards past the "74 pm"74 pm mark on the graph:

  • When the two hydrogen atoms are too close, each proton in each nucleus repels the other. This is a nuclear repulsion energy.

  • This energy of repulsion is conventionally positive, so we move upwards on the potential energy curve.

A molecule wants to be as stable as possible; if it is unstable, it breaks apart.

So, the molecule prefers to be at the "74 pm"74 pm mark, which balances the repulsive and attractive energies, giving us the potential energy of the "H"-"H"HH single bond once the bond forms:

-"436 kJ/mol"436 kJ/mol


This potential energy is the energy leftover, stored in the bond, after making the "H"-"H"HH bond and releasing excess energy.

If the bond breaks, the potential energy is absorbed back into the atoms as kinetic energy as the atoms move far apart.