Class 11 Chemistry Chapter 9 Hydrogen
Hydrogen is one of the important elements on the Earth. It is constituent of water which is basic need of life on Earth. In this blog we will discuss in detail about hydrogen, its occurrence, its properties and uses.
Occurrence of Dihydrogen
Dihydrogen is most abundant in universe. About 70% of total mass of universe contains hydrogen. Planets like Jupiter and Saturn contains mostly hydrogen. On earth, hydrogen is present in 0.15% by mass. However, in combined state it occupy 15.4% of Earth’s crust and oceans. Other than water, hydrogen occurs in carbohydrates, proteins, hydrides, hydrocarbons and other such compounds.
Position of hydrogen in periodic table
Hydrogen has atomic number 1. Moreover, the electronic configuration is 1s1. It is interesting to know that electronic configuration of hydrogen is similar to electronic configuration of alkali metals that is ns1. So it is possible to place hydrogen with alkali metals. However, every atom has the ability to donate or accept electron to achieve noble gas configuration. Hydrogen can gain one electron to achieve noble gas configuration. However this is property of halogen. This shows that hydrogen resembles with halogen. Thus, hydrogen can be placed with halogens. Since, the place of hydrogen was difficult to decide, it was placed separately on top of periodic table.
Hydrogen and its isotopes
Isotopes of Hydrogen
Isotopes are two or more form of same element, having same number of protons and different number of neutrons in the nucleus of atom. In case of hydrogen, it has three isotopes, Protium, Deuterium, Tritium.
Protium or 11H has one proton and zero neutron. Moreover, it is most abundant form of hydrogen.
Deuterium or 12H or D has one proton and one neutron. It is well known as heavy hydrogen. Terrestrial hydrogen contains 0.0156% of deuterium or Hydrogen Deuterium.
Tritium or 13H or T, has one proton and two neutron. It is present in very less amount on Earth, i.e., concentration of tritium is about one atom per 1018 atoms of protium. Moreover, tritium is radioactive and emits low energy β particles.
As the electronic configuration of isotopes are same, there chemical properties is also same. However, they show difference in the rate of reaction. For example, reaction of protium and chlorine is 13.4 times faster than deuterium and chlorine.
Physical Properties of Dihydrogen
Dihydrogen is colorless, odourless, tasteless as well as combustible gas. It is lighter than air. However, dihydrogen is insoluble in water. Here as some more physical properties of dihydrogen.
Properties of Hydrogen
Chemical Properties of Dihydrogen
- Reaction with halogens: Hydrogen reacts with halogens X2 and forms hydrogen halides HX. In case of Fluorine, reaction occurs even in dark, as fluorine is highly reactive. In case of Iodine, it requires catalyst to complete the reaction.
H2(g) + X2 ⟶ 2HX(g) (X = F, Cl, Br, I) - Reaction with dioxygen: Dioxygen and Dihydrogen reacts with each other to form water. This reaction is an exothermic reaction.
catalyst/ heating
2H2(g) + O2(g) ⟶ 2H2O (l) - Reaction with dinitrogen: Hydrogen reacts with dinitrogen thereby forming ammonia. This process is widely used for manufacture of ammonia called haber’s process.
Fe, 200 atm, 673K
2H2(g)+ N2(g) ⟶ 2NH3(g) - Reaction with metals: Hydrogen reacts with metals to form hydride.
H2(g)+ 2M(g) ⟶ 2MH(s) (M= metals) - Reaction with metal ions: dihydrogen have the ability to reduce some metal ions in aqueous solution into their metallic state.
H2(g)+ Pd2+(aq) ⟶ Pd(s) + 2H+ - Reaction with metal oxides: Dihydrogen reduces metal oxides of metals like iron and metals less active than iron to their respective metallic state.
heat
Fe2O4 + 4H2 ⟶ 2Fe + 4H2O
Uses of Dihydrogen
- Hydrogen is used in preparation of ammonia, which is starting material for manufacture of fertilizers like urea, ammonium sulphate, calcium ammonium nitrate, etc.
- Hydrogen is used in hydrogenation of oils to form edible fats.
- It is used in formation of metal hydrides. For example, LiH, CaH2, AlH3, GeH4, etc.
- Hydrogen is used for reducing heavy metal oxide to metals.
- In case of welding, oxyhydrogen torch and atomic hydrogen torch is used.
- Liquid hydrogen mixed with liquid oxygen is used as rocket fuel.
- It is used in fuel cell for generating electrical energy.
Keywords: Dihydrogen, Haber’s Process, Hydrogenation of oils, Protium, Deuterium, Tritium
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