Re: Can you make a water molecule with a hydrogyen molecule and O3?

You refer to the a reaction between hydrogen and oxygen, which you describe as 

2 H2 + O2 --> 2 H2O  (reaction 1)

and you ask about the reaction between hydrogen and ozone:

H2 + O3 --> H2O + O2   (reaction 2)

Can this reaction go? The answer is yes. But it has to be qualified with a "sort 
of".

The problem is that chemical reactions are a little bit more complicated than 
this when you look at the details. Reaction 1 describes an overall 
transformation. But it does not tell you that that reaction actually occurs in 
several steps, involving what is known as a "radical chain mechanism".

Hydrogen molecules cannot react directly with oxygen molecules at ordinary 
temperatures. The two gases can be mixed together, and nothing will happen -- for 
a start, anyway. But a reaction can be started by a catalytic surface, or some 
ultraviolet radiation, or a lot of heat, or by ions produced in a radioactive 
decay. Here is the usual way that a reaction between hydrogen and oxygen gases 
goes:

There are a few stray water molecules in the system. One of them gets broken up 
by some UV light or a cosmic ray or in an unusually high energy collision:

H2O --> H + OH (reaction 3)

H is a hydrogen atom; OH is a hydroxyl radical. Both are very reactive, and tend 
to react with the first molecule they bump into.

H + O2 --> HO2   (reaction 4)

HO2 is a hydroperoxy radical, which is also very reactive

OH + H2 --> H2O + H   (reaction 5)

HO2 + H2 --> H2O + OH   (reaction 6)

These reactions recycle the H and OH at the same time as they use up H2 and O2 
and produce water.

If we add reactions 4 and 5 and 6 together we get the same as reaction 1.

There are also other reactions that can produce extra OH, such as

H + O2 --> OH + O   (reaction 7)

O + H2 --> OH + H   (reaction 8)

These will help the reaction to go faster. If OH builds up too much, they will 
lead to an explosion.

If ozone is used instead of oxygen, your reaction 2 will go much faster and more 
readily, and there is a bigger danger of explosion. The main way the reaction 
would get started is

O3 + light --> O2 + O

Then we can have

O + H2 --> OH + H

and once OH and H are present

H + O3 --> OH + O2
OH + H2 --> H2O + H

If we add these last two reactions together we can see that H and OH are 
recycled, and your reaction 2 is the overall effect.