HYDROGEN AND ITS USES

HYDROGEN Cavendish discovered hydrogen in 1766. Lavoiser named it hydrogen, meaning water former. Hydrogen is a flammable gas; it burns in air to produce water. It is an important constituent of all acids and alkalis, combined with carbon. Hydrogen is found in natural gas, kerosene, gasoline and other petroleum products. It is also constituent of most other organic substances including proteins, carbonhydrates and fats which are essential components of all living matter. Laboratory Preparation of Hydrogen: In the laboratory, three methods are used in the preparation of hydrogen which are; Action of zinc (Zn) on an acid: dilute hydrochloric or tetraoxosulphate (vi) acid attacks metallic zinc with the liberation of hydrogen gas (no heating is necessary). Zn(s) + HCl(aq) → ZnCl + H2(g) Zn(s) + H2SO4(aq) → ZnSO4 + H2(g) Action of sodium (Na) on cold water: sodium liberates hydrogen from cold water. This reaction is very vigorous and should be carried out with extreme care using only a piece of sodium. 2Na(s) + 2H2O(L) → 2NaOH(aq) + H2(g) Action of iron (Fe) on steam: iron at red heat liberates hydrogen from steam, example; 3Fe(s) + 4H2O(g) ↔ Fe3O4(s) + 4H2(g). This reaction is a reversible reaction. Industrial Preparation of Hydrogen Preparation of hydrogen from water gas (Bosch process): water gas is mixed with excess steam and passed over a catalyst of iron (iii) oxide or chromium (ii) oxide at temperature of 400oC or 500oC. Hydrogen is produced and the carbon (ii) oxide formed in the water gas is converted to or oxidised to carbon (iv) oxide. CO + H2 + H2O → CO2↑ +2H2, this reaction occurs in the presence of catalyst, also, it is an exothermic reaction. This method is cheap, because cheap materials are used. Preparation of hydrogen from methane (natural gas): methane is heated with steam at about 900oC and passed over nickel as catalyst. A mixture of hydrogen and carbon (ii) oxide known as synthetic gas is formed CH4 + H2O(g) →CO(g) + 3H2(g) (synthetic gas) The synthetic gas formed is mixed with more steam and passed over iron (iii) oxide as catalyst at about 450oc CO(g) + 3H2(g) + H2O(g) → CO2(g) + 4H2(g) Electrolysis: another way of preparing hydrogen is by electrolysis, this method is more applicable where electricity is cheap, for example in countries where hydroelectric power is readily available. Physical Properties of Hydrogen Hydrogen is the lightest element known It is neutral to litmus paper Hydrogen is colourless and odourless in pure form It is slightly soluble in water Chemical Properties of Hydrogen Hydrogen reacts with metals to form ionic hydrides 2Na(s) + H2(g) → 2NaH(s) Hydrogen gives a pop sound when flame is applied to it. It burns with a blue flame to produce water. 2H2(g) + O2(g) → 2H2O(L) Uses of Hydrogen Hydrogen is used to produce ammonia that can be used in common household cleaning products. Hydrogen is used as a hydrogenating agent to produce methanol and convert unhealthy unsaturated fats and oils to saturated fats and oils. Hydrogen is used in the production of hydrochloric acid which is widely used in chemical industries. Hydrogen is used as a rotor coolant in electrical generators. Hydrogen gas is used to reduce many metallic ores. Hydrogen is used in the processing of petroleum products to breakdown crude oil into fuel oil and gasoline.