Wait so what's the malic acid for then?
Malic acid (C4H6O5) reacts with magnesium to produce hydrogen gas (H2). If you look at this earlier post, you see that @streamlover has explained the details of the reaction: magnesium + malic acid —> hydrogen gas + magnesium malate:
Mg + C4H6O5 —> H2 + MgC4H4O5
Because magnesium also reacts with water (H20), when you add magnesium to a solution of malic acid in water, you also get to a lesser degree the reaction: magnesium + water —> hydrogen gas + magnesium hydroxide:
Mg + H2O —> H2 + Mg(OH)2water
So there are two separate reactions going on when you drop magnesium into an aqueous solution of malic acid: one reaction with the malic acid, and another simultaneous reaction with the water.
However, because at room temperatures the reaction of magnesium with water is slow, and because at room temperatures the reaction of magnesium with malic acid is more vigorous, most of the hydrogen gas produced will come from the reaction with malic acid.
You can see this for yourself: if you drop a piece magnesium ribbon into boiling water from the kettle, you will see tiny little bubbles of H2 gas very slowly forming on the surface of the magnesium ribbon. But the reaction of magnesium with water at relatively low temperatures like 100ºC is very slow, so you barely see any bubbles at all.
If you now drop in some malic acid or citric acid powder into that hot water, instantly you get loads more bubbles of H2 gas forming on the magnesium, because the reaction of magnesium with these acids is a lot more vigorous.
However, that's the case at relatively low temperatures of100ºC. But if you dropped some burning magnesium ribbon into pure water (with no acid in the water), because magnesium ribbon burns at a very high temperature of 3100°C, now you get a very vigorous reaction between the magnesium and the pure water, due to the high temperature. If you do this experiment, you will see that magnesium ribbon burns faster and more vigorously underwater than it does in air.
You can see how a pile of burning magnesium almost explosively reacts with water in
this video.
So my idea is that you could make hydrogen water by dropping into a beer bottle filled with pure water some burning magnesium ribbon, very quickly closing the bottle lid, so that you create pressure. You would have to be quick, because magnesium ribbon burns very fast in water. Hopefully the beer bottle will not explode!
Edited by Hip, 29 July 2016 - 02:52 PM.