Hydrogen Gas Formula Structure, Properties, Uses, Sample Questions (original) (raw)

Last Updated : 21 Dec, 2023

Hydrogen gas consists of only two hydrogen atoms. It is the lightest element and is present in group 1 of the periodic table. Hydrogen gas is non-toxic gas but highly combustible. Hydrogen gas is colorless, tasteless, and odorless and is represented by the symbol H. Its atomic number is 1.

In standard conditions, the Hydrogen atom exists as a diatomic molecule with the molecular formula H2. Hydrogen is not carcinogenic, non-toxic, and is recognized as a clean-burning fuel. It is produced from Coal and Water. The other name for Hydrogen gas is Molecular Hydrogen. It is stored as compressed gas or as liquid and is used in the production of polyurethane plastics and is suitable for internal combustion engines in automobiles.

Preparation of Hydrogen gas

• When Zinc reacts with Hydrochloric acid to produce Hydrogen gas and Zinc chloride.

**Zn + 2HCl ⇢ ZnCl 2 + H 2

• On reaction between Zinc and Sulphuric acid gives Zinc sulfate and Hydrogen gas.

**Zn + H 2 SO 4 ⇢ ZnSO 4 + H 2

Structure of Hydrogen Gas

Physical Properties of Hydrogen Gas

• Hydrogen gas is colorless, odorless gas.
• The molecular weight of Hydrogen gas is 1.00794.
• The density of Hydrogen gas is 0.0893 g/L.
• The melting point of Hydrogen gas is -259.2 °C.
• Its boiling point is -252.9 °C.
• The solubility of hydrogen gas in water is 1.62 mg/L at 21 °C.

Chemical Properties of Hydrogen Gas

• Nitrogen in the atmosphere reacts with hydrogen gas to produce Ammonia. The chemical reaction is given below

**N 2 + 3H 2 ⇢ 2NH 3

• In the production of Methanol, Hydrogen gas is involved. It is not separated from the synthesis gas stream in the synthesis reaction. The chemical reaction is given below

**CO + 2H 2 ⇢ CH 3 OH

• Hydrogen reacts with chlorine to yield Hydrogen Chloride (HCl)

**H 2 + Cl 2 ⇢ 2HCl

• Hydrogen gas at a certain temperature and pressure reduces the metal oxides and metallic salts into metals.

**H 2 + FeO **⇢ Fe + H 2 O

**H 2 + PdCl 2 ⇢ Pd + 2HCl

Uses of Hydrogen Gas

• Hydrogen gas is used in filling weather observation balloons along with helium gas in equal volumes.
• It is used in internal combustion engines in automobiles.
• The oxy-hydrogen flame generates a lot of heat, such that it is used for welding and cutting metals.
• It is used in converting edible vegetable oils into Vanaspati ghee.
• Hydrogen gas is used in the production of polyurethane plastics.

Sample Problems

**Problem 1: How Hydrogen gas is prepared?

**Solution:

Hydrogen gas is prepared in many ways. Few are listed below

• **Electrolysis of Water In this process, electric current is passed through water to split into hydrogen and oxygen.
• The other way to prepare hydrogen gas is reacting natural gas with steam of very high temperature to produce a mixture containing Hydrogen gas with Carbon monoxide and carbon dioxide.

**Problem 2: What are the uses of Hydrogen gas?

**Solution:

Hydrogen gas is used to produce polyurethane plastics. It is also used in converting edible vegetable oils into Vanaspati ghee. Used by black smith. It is also used in automobile industry as a furl for internal combustion engines.

**Problem 3: What happens when Hydrogen reacts with Halogens?

**Solution:

Hydrogen reacts with halogens such as Fluorine, Chlorine at room temperature to form corresponding Hydrogen halides i.e. Hydrogen Fluoride, Hydrogen Chloride etc. which are very harmful acids.

**Problem 4: What happens when Hydrogen reacts with Alkali metals?

**Solution:

Hydrogen reacts with alkali metals like Sodium, Potassium to produce respective hydrides like Sodium Hydride, Potassium Hydride etc.

**H 2 + 2Na ⇢ 2NaH

**Problem 5: In which form does hydrogen gas exist in nature.

**Solution:

It is available in plenty amount. In nature, Hydrogen gas is available in the form of water (H2O) which consists of 2 hydrogen atoms and 1 oxygen.

**Problem 6: What happens when Hydrogen reacts with Metal oxides?

**Solution:

Hydrogen gas reacts with metal oxides like Iron oxide at high temperature and pressure to reduce the metallic oxide into metals. The sample chemical reaction is given below for FeO.

**H 2 + FeO ⇢ Fe + H 2 O

**Problem 7: What happens when Hydrogen reacts with Metallic salts?

**Solution:

Hydrogen reduces metallic salts to metals at certain temperature and pressure. So Hydrogen gas reduces Palladium chloride to Palladium metal.

**H 2 + PdCl 2 ⇢ Pd + 2HCl