# Using Le Chatelier's Principle to Change Mechanical Energy to Chemical Energy

I was interested in an application of Le Chatelier's principle, where an increase in pressure could result in a decrease in the moles of gas.

In particular, a situation where when the pressure increased, it drove the reaction in one direction (towards fewer moles), but when the pressure was lower, then the reaction went the other direction.

What pairs of two reactive room-temperature gases can both combine to make a third room-temperature gas where the change in chemical energy can be used to store the energy from the work done on the system by compression?

So far, I've found these possible candidates:

\begin{align} \ce{2 SO3 &<=> 2 SO2 + O2}\\ \ce{2 CO2 &<=> 2 CO + O2}\\ \ce{2 NH3 &<=> N2 + 3 H2} \end{align}

I'm imagining a situation where a mixture of gasses could be compressed to a significant fraction of its original volume without too big of an increase in temperature.

Maybe a catalyst might be critical to make the activation energy less of an issue.

I don't know if this is possible, though.

I'm teaching a module on energy conversion.

We have 5 common types of energy: mechanical, electrical, thermal, chemical and light. And we are discussing conversions between them.

The example of changing mechanical energy to chemical energy I had been using was the compression of graphite to make diamonds. I wasn't happy with this one, though.

Then I half-remembered something from my college chemistry class where the direction of a chemical reaction could be shifted by changing the pressure or the temperature, and I wanted to investigate that idea.

That's the inspiration for this question. If this process is useful, all the better. If it's not, then it's a way to introduce some important concepts and something they'll see later in their college chemistry class.