How would one combine the gasses oxygen and hydrogen to form water?

Well, I know it would be two parts hydrogen to one part oxygen, but how the process actually occurs, I can’t tell you.

Read this.

The splitting and recombining of hydrogen and oxygen molecules is essentially how fuel cells work.

Yes, it would be pure water.

Set fire to the mixture.

Obviously, I don’t recommend doing this with large quantities of both substances.

duct tape

You could mix the gasses together and light a match to start the chemical reaction.

Or, you could mix an acid and a base, like vinegar and baking soda, which creates carbon dioxide, sodium acetone and water.

Combustion. The safest way is to have a slow release of hydrogen into a tank of pure oxygen, with a small flame to stimulate the reaction. If you just burn them as mixed gasses, it looks something like the Hindenburg. This produces pure water vapour. To form pure liquid water, you need to channel the vapour into a cool flask for it to condense.

Not homework, surely?

it looks something like the Hindenburg. – my organic chemistry textbook included detailed instructions – I kid you not – for making nitroglycerin. It ended with the injunction, DO NOT ATTEMPT THIS IN THE LABORATORY. Mind you, this is some 50 years ago. Back on topic, another method is to pass an electric current through a mixture of hydrogen and oxygen, but I have never seen it done.

@bea2345 Ahh, the good old days…they sure sound nice.

@Jeruba No its not, the question is just a facet of a process for water purification that I had thought out but didn’t fully understand the science behind.

O @Jerubae of little faith!

Burn them.

Very carefully.

Just pour them in a jar, put on the lid, and shake.

The simplest way is combustion, you don’t even need pure oxygen. The combustion product is pure water.

Lightning

I wonder if you can make commerical drinkable pure water that way?

@talljasperman It is not economically viable. To form hydrogen industrially, fossil fuels are passed through a cracking mechanism. Its been three years now since I studied this, so I don’t remember the details. Since the supply of fossil fuels is limited, it would not be viable for producing water. It is also a very expensive process, so it is usually reserved for further reactions such as forming nitrates like ammonia for fertilisers etc.

The amount of water formed by this process is also quite small, because hydrogen and oxygen both exist in a gaseous state at room temperature, and water is a relatively dense liquid. The volumes of gas required would be huge, with a very small yield of water.

http://www.haverford.edu/educ/knight-booklet/electrolysis.htm

This is a setup for both electrolyzing water to form hydrogen and oxygen, and for synthesizing them again. I have done this before with a rather different apparatus. I recommend outfitting this setup with a closed system to store the gases, which will make the water vapor condense more quickly and controllably. Don’t expect to get very much water from the synthesis though; 2 liters of hydrogen and 1 of oxygen gases made only a few drops when I did it. It requires a tremendous amount of energy to electrolyze a significant volume of water.

For the synthesis, a spark works best, a flame is more difficult to control in a closed system, in my experience.

The electrolysis of water is a more viable option for converting excess PV or wind generated elecric power into hydrogen as a form of “green fuel” storage. Reverse osmosis is a more economical option for purifying brackish or polluted water.

Does reverse osmosis require you to change the membranes?

@aeschylus RO membranes, if properly maintained, last a long time. The process equipment washes out the contaminants. It’s not like a filter that “traps” the contaminants, although sometimes a prefilter is used to remove gross contamination before the RO stage. These filters can be backwashed and reused (in large commercial-scale applications).