Preparation of Hydrogen involves various steps.Hydrogen is a unique element as it shows resemblance to both alkali metals and halogens. It is a very reactive element and forms many hydrides and other compounds. It is found in the plant and animal tissues. The preparation of hydrogen can be broadly classified as:
Laboratory preparation of hydrogen:
When granulated zinc is reacted with a dilute hydrochloric acid, hydrogen is obtained. This is the most common procedure of producing hydrogen. We can also prepare hydrogen by reacting zinc with aqueous alkali. The following reaction will make this clear:
\(~~~~~~~~~~~~~~~~~~~\)Zn + 2NaOH → Na2ZnO2 + H2
A commercial preparation of hydrogen:
There are many ways in which it is prepared commercially. Following are some of the methods used generally.
a. When acidified water is electrolyzed using platinum electrodes, hydrogen is produced.
b. To obtain hydrogen of high purity we can electrolyze warm aqueous barium hydroxide solution between nickel electrodes.
c. When stream reacts with hydrocarbons at very high temperatures in the presence of some catalyst, hydrogen is formed. For example, methane reacts with water at 1270K in presence of nickel to give carbon monoxide and water.
\(~~~~~~~~~~~~~~~~~~~\) CH4 (g) + H2O(g) → CO(g) + 3H2(g)
The mixture of carbon monoxide and water is popularly called as water gas. This water gas is used for the synthesis of methanol and many hydrocarbons and so it is also known as the synthesis gas or ‘syngas’. This syngas is prepared from sewage, sawdust, scrap wood etc. We can also produce syngas from coal and this process is known as ‘coal gasification’. We can increase the production of hydrogen gas by reacting carbon monoxide of syngas with a stream in the presence of iron chromate as catalyst and temperature of 673K.
\(~~~~~~~~~~~~~~~~~~~\) CO(g) + H2O(g) → CO2(g) + H2O(g)
The above reaction is known as water gas shift reaction. As of now the maximum percentage of the hydrogen gas is produced from petrochemicals, some from coal and a very little percent from electrolysis of aqueous solution.
So far we have seen how to make hydrogen in the laboratory and commercially, for more details kindly install the Byju’s learning app.