Hydrogen is the first element of the periodic table and it is the most abundant element in the universe. On earth it is the ninth most abundant element. According to scientists the sun and the other stars are composed largely of hydrogen. It has a wide range of chemical and physical properties. Its old name is inflammable air. It also forms a wide range of compounds. Its most important compound is water which covers about three fourth part of the earth. In addition to that, compounds of carbon which are in the form of natural gas and petroleum contains large amount of hydrogen in them. It is an essential component of many organic compounds which produce biological materials. These include proteins, carbohydrates and lipids, etc.
In the laboratory, hydrogen is prepared by the action of dilute mineral acids with moderately reactive metals. The most commonly used acids are dilute sulphuric acid of hydrochloric acid and the metal is zinc. Dilute nitric acid is not used for the preparation of hydrogen as it is a strong oxidising agent and will produce hydrogen only when it reacts with magnesium. Calcium hydride is hydrolysed to give calcium hydroxide with the liberation of hydrogen gas.
In the laboratory, hydrogen is prepared by the action of dilute mineral acids with moderately reactive metals. The most commonly used acids are dilute sulphuric acid of hydrochloric acid and the metal is zinc. Dilute nitric acid is not used for the preparation of hydrogen as it is a strong oxidising agent and will produce hydrogen only when it reacts with magnesium. Calcium hydride is hydrolysed to give calcium hydroxide with the liberation of hydrogen gas.
