Hydrogen is the simplest molecule possible, a covalently bonded two atoms of Hydrogen.
This is an odourless colourless gas, but in all probability, this gas is never in the air due to its high rate of combustion with Oxygen to form water. In fact, the test for Hydrogen is that reacts with a pop due to the fact that the reaction is so fast.
Preparation
The preparation of hydrogen is a straightforward reaction, where displacement reactions are used. Due to the fact that a number of metals are higher up in the reactivity series, it is easy to find a metal that will displace Hydrogen from an acid, such as Magnesium, Zinc and Iron.
Mg + 2HCl → MgCl2 + H2
Industrial Preparation
In industry hydrogen is produced using methane and steam in a two-step reaction:
CH4 + H2O(g) → CO + 3H2
CO + H2O(g) → CO2 + H2
Reducing properties
It must be noted that Hydrogen can be used as a reducing agent to produce pure metals when passed over heated metal oxides, such as CuO and PbO2. The metal oxides have to be heated.
CuO + H2 → H2O + Cu
Fuel cell
The reaction of Hydrogen with water is a very exothermic reaction, and a lot of research is being made so that this heat that is given off is used to generate power or electricity. This is due to the fact that the product of reaction would be water, which would have no detrimental effect on the environment. Disadvantages include the fact that the reaction needs to be carefully controlled so that it would be safe to use and that recharge areas might not be very stable and therefore expensive together with the fact that at the moment very these can be found in a small number of stations around the world.