question 1. There's no deep intrinsic reason for any of the O
2 or H
2 to be lost. In practice some will be, but not much if the apparatus isn't leaky. That's a contrast to the energy balance. The work put in to electrolyze the water will always be bigger than the work gotten back from the reaction, for fundamental thermodynamic reasons.
2. Ordinary burning of either hydrogen or gasoline requires oxygen. The carburetor or fuel injector on a car is designed to mix in just the right amount of oxygen from air. The burning in the Sun is of an entirely different type. It consists of nuclear reactions, making new types of atoms. Ordinary burning is a type of chemical reaction, in which fixed types of atoms recombine into different types of molecules.
3. I'm not sure- it depends on the oxygen concentration. Too much hydrogen actually suppresses the explosion. I've seen, however, liquid oxygen react explosively with some ordinary solvent, probably acetone.
Mike W.
(published on 04/01/2008)