Inorganic Chemistry

 Hydrogen gas

Symbol:H.          Atomic mass:1.008amu

Atomic number:1.           Valency:1

Molecular weight:2.016amu

Freezing point: -259⁰C

Boiling point: -253⁰C

An English scientist,Henry Cavendish discovered hydrogen gas in 1776 and named it inflammable gas because of its burning property in the air.

In 1783,French scientist Lavoisier gave the name Hydrogen to it. Because it forms water while burning.

Hydrogen is the lightest and simplest element. Hydrogen atom is composed of proton and an electron.                                                                                                                                                                                                As it is highly reactive gas, it is not found freely in nature but found in the compound or in combination with various other elements in substance like acid ,water, hydrocarbon,petrol,oil,etc.

This gas is abundant in the sun and star and paly significant role to produce heat and light by nuclear fusion reaction.

General method of preparation of hydrogen gas

1.When metal react with water, hydrogen gas is formed.

Na+H2O  --------------- Na2O +H2

2.When water get electrolysis its ions are separate and hydrogen gas is produced.

Laboratory preparation of hydrogen gas

Requirements:

1.Apparatus required: Woulfe's bottle, Thistle funnel, Delivery tube, Gas jar, Water trough, and Beehive shelf

2. Chemical required: Granulated zinc, Dilute sulphuric acid(H2SO4) or dilute hydrochloric acid(HCL)

Principle:

Hydrogen gas can be produce in laboratory by reaction between granulated zinc and dli.hydrochloric acid or dil.sulphuric acid. i.e.

Zn +  2HCl    -------------------   ZnCl2+ H2

Zn +  H2SO4    --------------  ZnSO4+ H2

Procedure:                                                                                  Firstly, Woulfe's bottle is taken and put some granulated zinc inside it. Thistle funnel and delivery tube is placed and air tight by cork. Delivery tube is placed at gas jar in beehive shelf as shown in figure. Here at Woulfe's bottle reaction takes place and hydrogen gas is started to produced. Hydrogen gas ice collected by downward displacement of water because it is lighter than air and insoluble in water.

Properties of atomic hydrogen.

1.It has very short half-life of 0.3 sec only ,it is very unstable in nature.

2.It is reactive in nature. So,it immediately forms molecular hydrogen.

3.It acts as powerful reducing agent and can reduce metal chlorides and oxides to metals.

Agcl+ H --------> Ag + HCl

CuO + 2H -------> Cu + H2O

HgCl2 + 2H ------> Hg + 2HCl.

2. Nascent Hydrogen.

Nascent stand for newly born. The hydrogen produced at the time of it's birth as a result of chemical reaction in solution in contact with substance to be reduced is called nascent hydrogen. Nascent Hydrogen consists of atom of hydrogen and denoted by symbol [H]. It is more reactive as well as strong reducing agent than molecular hydrogen. Following reaction support this statement.

1. Reduction of potassium permanganate

KMnO4+H2So4 +H2 ------- no reaction

Zn +H2So4 ------- ZnSo4 +2[H]

2KMnO4+3H2So4+10[H]------------  K2So4+2MnSo4+8H20