Preparation
Electrolysis
Hydrogen is prepared by the electrolysis of brine. It is prepared at the cathode.
Steam reforming
CH4 + H2O(g) → CO + 3H2 (Ni catalyst 700oC)
CO + H2O(g) → CO2 + H2 (Fe catalyst 400oC)
K2CO3 + H2O + CO2 → 2KHCO3 (to remove CO2 from the mixture)
Acids + metals
An acid + a metal above Hydrogen in the E.C.S. will produce hydrogen as a product.
Ionic hydrides + water
Ionic hydrides react with water to liberate hydrogen.
Reactions
Saturation reactions
Hydrogen is used to saturate organic molecules such as alkenes. This is done by the aid of Nickel catalyst and a temperature of 140oC.
Hydride formation
Reactive metals and non-metals react with hydrogen to produce hydrides, such as NaH, KH, MgH2, H2O, H2S and HCl
Ammonia
Ammonia is prepared via the Haber process using iron as a catalyst, high pressures and a temperature of around 400oC.
Reducing agent
Hydrogen is a good reducing agent, reacting with Sulfur, Oxygen and halogens.
It also reduced CuO to Cu via the following reaction:
H2 + CuO → Cu + H2O
Nascent hydrogen
The hydrogen gas, which is just liberated as a result of a chemical is called nascent hydrogen or newly born hydrogen.
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Ionic Hydrides
Simple hydrides
A simple hydride is when a metal reacts with hydrogen to produce a simple ionic hydride, such as NaH.
Complex hydrides
A complex hydride is when the hydride reacts with an electron deficient atom, such as Aluminium to form a negatively charged ion. These are normally very reactive.
4LiH + AlCl3 → LiAlH4 + 3LiCl3
Covalent Hydrides
These are the products of the reaction between a non-metal and hydrogen.
Interstitial Hydrides
Hydrogen is a very small molecule, and therefore these can fit in small places, such as transition metal lattices.
Isotopy
There are 3 types of isotopes for hydrogen;
All of these isotopes react in the same way, and therefore any reaction with D2O would be as if one is reacting with H2O.
Deuterated Compounds
Preparation of deuterated compounds can be prepared using the same reactions as usual, using deuterated starting materials.
DCl
SOCl2 + D2O → SO2 + 2DCl
ND3
Mg3N2 + 6D2O → 3Mg(OD)2 + 2ND3
C2D2
CaC2 + D2O → Ca(OD)2 + C2D2