Hydrogen

Hydrogen

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.

Reaction

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.

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;

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.

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