Re: [Phys-L] Electrolysis under Pressure

[John Denker <jsd@av8n.com>]

In the context of:

> > A friend has reverted to childhood by wishing to make balloon bombs using
> > electrolysis of waster.  I suggested that compression of the gasses would
> > "slow" the electrolysis due to the Le Chatelier principle.

On 06/15/2014 11:34 AM, rjensen@ualberta.ca wrote:

> This reaction is not in equilibrium, so le Chatelier's principle
> doesn't apply. The gas pressure will not effect the electrolysis rate.

I wouldn't have said that.  The reaction /could/ be carried
out under close-to-equilibrium conditions, in which case
you /could/ see the effect of pressure.

There is energy in the pressurized products, and this enters
directly into the energy budget of the reaction.  In the
case of electrolysis, I would expect to see it in the cell
voltage.  In other situations, I would expect it to shift 
the equilibrium point.

As a familiar example, consider the equilibrium between 
gaseous CO2 and an aqueous solution of dissolved CO2 plus 
carbonic acid.  The equilibrium point is a strong function
of pressure.
 -- Hint:  champagne
 -- Hint:  seltzer water
 -- Hint:  mentos + diet coke

===========================

As a separate matter, Le Châtelier's so-called principle is
not the smart way to think about the issue.  In his lifetime, 
Le Châtelier gave two inconsistent statements, one of which 
is trivially tautological, and the other of which is just 
wrong.  For details, see
  http://www.av8n.com/physics/thermo/spontaneous.html#sec-le-chatelier