How can electrolysis be used to separate water from hydrogen and oxygen?

Answer 1

Nothing, until you light a match. Water can be decomposed into H2 and O2. These gases are stable at room temperature, but H2 is very flammable. In the presence of O2, H2 will combust and form water again.

Answer 2

It sounds like you are referring to electrolysis.

In pure water, there is an equilibrium between whole water molecules and dissociated H+ and OH- ion (or H3O+ and OH-, depending on how you want to represent it). At the negatively charged cathode, a reduction reaction takes place where the reaction is:

2 H+(aq) + 2e− → H2(g) or 2 H2O(l) + 2e− → H2(g) + 2 OH-(aq) if you want to write the reaction as a base reaction.

At the corresponding positively charged anode, the reaction is an oxidation - where the reaction is:

2 H2O(l) → O2(g) + 4 H+(aq) + 4e− or 4 OH- (aq) → O2(g) + 2 H2O(l) + 4 e− if you want to write the equation as a base reaction.

Obviously more hydrogen gets generated by this reaction than oxygen - which is exactly what the stoiciometry would predict, with the overall reaction being:

2 H2O(l) → 2 H2(g) + O2(g)

To put it another way - hydrogen ions in the water migrate to the cathode where they are supplied with electrons to form hydrogen gas while hydroxide ions migrate to the anode where they surrender electrons to form new hydrogen ions and oxygen molecules. The reaction at the electrodes are actually a bit more complicated with both electrodes converting ions to gas molecules AND water molecules into fresh ions that can migrate through the water to the opposite electrode.

Answer 3

When water is decomposed electrolytically, the hydrogen atoms in water are reduced, and the oxygen atoms are oxidized. The reaction is:

2H2O ---> 2H2 + O2

The oxidation state of oxygen in water is -2, and the oxidation state of hydrogen is +1. However, the oxidation state of both hydrogen and oxygen in the products is 0 (zero). Hydrogen thus gains 1 electron (2 total to form H2), and oxygen loses 2 (4 total to form O2).

So H2 is evolved where electrons are being put into the water, which by definition, is at the cathode. At the cathode, electrons go from the electrode into the water to reduce water:
4H2O(l) + 4e- → 2H2 (g) + 4OH-(aq)

At the anode, the oxidation of water occurs, and electrons go into the electrode:
2H2O(l) → O2 (g) + 4H+(aq) + 4e-

Therefore, O2 is evolved at the anode, and H2 is evolved at the cathode.

Answer 4

electricity is pumped though the water to decompose the water into pure hydrogen and pure oxygen

Answer 5

In the electrolysis of water, hydrogen and oxygen atoms are separated. They form their respective gases and escape the water molecules.

Answer 6

During electrolysis water molecules are split into their constituent atoms, Oxygen gas is produced at one electrode and Hydrogen gas is produced at the other.

Answer 7

Electrical current is used to spilt water molecules into their constituent gases. Hydrogen is produced at one electrode and oxygen is produced at the other.

Answer 8

During the process of electrolysis, the ions that are formed become cations which when dissolved into water, the ions are dissolved and are terminated.