[Chemistry Class Notes] on Preparation of Hydrogen and Its Uses Pdf for Exam

Universally, Hydrogen is the most abundant element. The Sun and the other stars are composed mainly of hydrogen. According to their estimation, 90% of the atoms in the universe are hydrogen atoms. Hydrogen is the component composed of more compounds compared to any other element. Also, water is the most abundant hydrogen compound that is found on Earth. Hydrogen is also an essential part of petroleum, many minerals, sugar, fats, cellulose and starch, oils, acids, alcohols, and thousands of other substances.

 

Hydrogen is a colorless, tasteless, odorless, and nonpoisonous gas at ordinary temperatures consisting of the diatomic molecule H2. Since hydrogen forms covalent compounds with most nonmetallic elements readily, most of the hydrogen element on Earth exists in molecular forms like water or organic compounds.

 

Hydrogen Preparation Methods

Preparation of Hydrogen involves multiple steps. Hydrogen is a unique element because it shows resemblance to both halogens and alkali metals. It is a reactive element and forms many hydrides and other compounds. It is found in a considerable amount in the plant and animal tissues. The hydrogen preparation methods can be given broadly as,

1. Preparation of Hydrogen by Laboratory method

2. Preparation of Hydrogen by a commercial preparation method

3. Industrial preparation of Hydrogen

 

1. Preparation of Hydrogen by Laboratory Method

The laboratory preparation of Hydrogen can be explained briefly as below.

 

This is a method of preparation of hydrogen that is used frequently. Hydrogen is produced when granulated zinc is reacted with dilute hydrochloric acid. This is a general procedure for producing hydrogen. Besides, hydrogen can also be prepared by reacting zinc with aqueous alkali. The following reaction explains it by making this clear.

 

[Zn + 2NaOH rightarrow Na_2ZnO_2 + H_2]

 

2. Preparation of Hydrogen by a Commercial Preparation Method

There are different ways in which hydrogen is prepared commercially, and this is another method of preparation of hydrogen. The following are some of the generalized methods used.

1. Hydrogen is produced when the acidified water is electrolyzed by using the platinum electrodes.

2. To obtain high purity hydrogen, we can electrolyze the warm aqueous barium hydroxide solution between the nickel electrodes.

3. Hydrogen is also formed when the stream reacts with hydrocarbons at specifically high temperatures in the presence of some catalyst. For example, methane reacts with water at 1270K in the presence of nickel to produce carbon monoxide and water.

 

[CH_4 (g) + H_2O (g) rightarrow  CO(g) + 3H_2 (g) ]

 

The carbon monoxide and water mixture are popularly known as water gas. This water gas is used in synthesizing methanol and many hydrocarbons, and thereby, it is also referred to as ‘syngas’ or synthesis gas. This synthesis gas is prepared from sewage, scrap wood, sawdust, and the related materials. We can also make syngas from coal, and this process is called ‘coal gasification.’ The increase of the production of hydrogen gas can be done by reacting carbon monoxide of synthesis gas with a stream in the presence of iron chromate as a catalyst at a temperature of up to 673K.

 

[CO (g) + H_2O (g) rightarrow  CO_2 (g) + H_2O (g) ]

 

The above-given reaction is known as the water-gas shift reaction. Currently, the maximum percentage of the hydrogen gas is formed from petrochemicals, some from coal, and a tiny percent from the electrolysis of an aqueous solution.

 

3. Industrial Preparation of Hydrogen

An essential industrial method for the production of hydrogen is the catalytic steam-hydrocarbon process. The gaseous or vaporized hydrocarbons are treated with steam at high pressure over a nickel catalyst at 650°- 950° C to form carbon oxides and hydrogen.

 

[C_nH_{2n+2} + nH_2O rightarrow nCO + (2n + 1)H_2 ];

[C_nH_{2n+2} + 2nH_2O rightarrow nCO_2 + (3n + 1)H_2 ];

 

The primary reaction products are further processed in different ways based on the hydrogen’s desired application. One more important hydrogen production process is the non catalytic partial oxidation of hydrocarbons under elevated pressures.

 

[C_nH_{2n+2} + (frac{n}{2}) O_2 rightarrow nCO + (n + 1)H_2 ]; 

 

This process needs a feed system for delivering accurate oxygen and fuel rates, individual design burners to give rapid mixing of the reactants, a cooling system, and a refractory-lined reactor to recover heat from the effluent gasses. The latter process is exothermic (producing heat) compared to the endothermic (absorbing heat) steam-hydrocarbon process.

 

Uses of Hydrogen (Dihydrogen) 

• Hydrogen is used in the synthesis of ammonia which is further used to manufacture nitric acid and nitrogenous fertilizers.

• Dihydrogen is used in the manufacturing of vanaspati fat by the hydrogenation of vegetable oils (polyunsaturated) like cotton seeds, soya beans, etc.

• It is used to manufacture a bulk of organic chemicals, especially methanol. CO (g) combines with 2H2 (g) in the presence of a cobalt catalyst to give methanol.

• It is largely used to manufacture metal hydrides.

• Hydrogen is useful to prepare hydrogen chloride, which is a highly useful chemical.

• It is used to reduce heavy metal oxides to metals in metallurgical processes.

• Oxyhydrogen and atomic hydrogen torches are used for welding and cutting purposes. Atomic hydrogen atoms are produced by the dissociation of dihydrogen using an electric arc that is allowed to settle on the surface to be welded to produce a high temperature of 4000K.

• In space research, it is used as rocket fuel.

• Hydrogen is used to generate electric energy through fuel cells. This form of energy has numerous benefits over conventional fossil fuels and other forms of energy. It does not release any harmful substances into the environment causing air pollution. It produces greater energy per unit mass of fuel as compared to gasoline and other fuels.

 

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