In the previous section,
we saw the structure and chemical properties of hydrogen peroxide. In this section,
we will see it's storage and uses. Later in this section, we will see heavy water and hydrogen economy also.
Storage of hydrogen peroxide
This can be written in 5 steps:
1. Hydrogen peroxide decomposes slowly on exposure to light.
2H2O2 (l) ⟶ 2H2O (l) + O2 (g)
2. The reaction in (1), is catalyzed by metals. So it is not possible to store H2O2 in metal containers.
3. The reaction in (1), is catalyzed also by alkali ions in glass. So it is not possible to store H2O2 in glass containers.
4. Due to these reasons, we use wax lined glass or plastic vessels to store H2O2.
5. Some additional precautions are to be taken:
♦ Urea can be added as a stabilizer.
♦ It must always be stored in dark.
♦ It must be always kept away from dust. If it comes into contact with dust, explosive decomposition may occur.
Uses of hydrogen peroxide
This can be written in 10 steps:
1. Hydrogen peroxide can be used as a hair bleach.
• Hair bleaching is a process for changing the color of hair. It must be used only under the guidance of experts.
2. Hydrogen peroxide can be used as a mild disinfectant.
• Disinfectants are used to kill germs on non living surfaces like table tops, floors etc., It must be used only under the guidance of experts.
3. Hydrogen peroxide can be used as an antiseptic.
• Perhydrol is the trade name of such an antiseptic.
• Antiseptics are used to kill microorganisms on the skin. It must be used only under the guidance of experts.
4. Hydrogen peroxide is used in the manufacture of sodium perborate and per-carbonate. They are used in high quality detergents.
5. Hydrogen peroxide is used in the synthesis of hydroquinone.
• The word synthesis means a chemical reaction between simple substances to form a complex substance.
• Hydroquinone is a skin lightening agent. It must be used only under the guidance of experts.
6. Hydrogen peroxide is used in the synthesis of tartaric acid.
7. Hydrogen peroxide is used in the synthesis of certain pharmaceuticals.
• Pharmaceuticals are substances used as medicinal drugs.
• Cepholasporin is an example. It must be used only under the guidance of experts.
8. Hydrogen peroxide is used in the synthesis of certain food products.
9. Hydrogen peroxide has industrial use as a bleaching agent.
• Bleaching agent is a substance which can lighten or whiten other substances.
• Hydrogen peroxide is used as bleaching agent for textiles, paper pulp, leather, oils, fats etc., It must be used only under the guidance of experts.
10. Hydrogen peroxide is used in environmental chemistry:
(i) To treat domestic and industrial effluents. Effluents are liquid waste sent out from factories.
(ii) Oxidation of cyanide to reduce it’s toxicity.
(iii) Restore aerobic conditions to sewage wastes.
• Aerobic condition is a condition in which free oxygen or dissolved oxygen is available in the sewage.
• Presence of oxygen helps to achieve effective treatment of the sewage.
Heavy water
Some basic details can be written in 3 steps:
1. We know that, a water molecule has two H atoms and one O atom.
• But in a heavy water molecule, deuterium atoms are present in the place of H atoms.
2. So the molecular formula of heavy water is D2O
3. The mass number of H is 1. But the mass number of D is 2.
• So D2O will be heavier than normal water.
• Ice made from heavy water will sink in normal water.
Uses of heavy water
This can be written in 3 steps:
1. Heavy water is used as a moderator in nuclear reactors. This is because, heavy water has the ability to slow down neutrons. Also it does not absorb neutrons.
2. Heavy water is used in exchange reactions so as to study the reaction mechanism.
• We have seen the application of deuterium to study the Haber process in a previous section. See fig.7.4 in section 7.3.
3. Heavy water is used to prepare other deuterium compounds. Some examples are given below:
CaC2 + 2D2O ⟶ C2D2 + Ca(OD)2
SO3 + D2O ⟶ D2SO4
Al4C3 + 2D2O ⟶ 3CD4 + 4Al(OD)3
Dihydrogen as a fuel
Some basics can be written in 7 steps:
1. When dihydrogen burns in air, a large amount of energy is released.
2H2 + O2 ⟶ 2H2O + Energy
• One gram of dihydrogen can release 143 kilo joules of energy.
• One gram of octane (petrol) can release only 47 kilo joules of energy.
2. When dihydrogen burns in air, no harmful pollutants are produced.
• When petrol burns in air, CO2 and many other pollutants are produced.
3. So it is clear that dihydrogen is a very good fuel.
• But it’s storage and transportation are difficult.
4. Hydrogen can be stored in gaseous form. For that, very high pressure is applied to compress the gas. So the cylinders carrying the gas will have to withstand very high pressure. Such cylinders will be very heavy. Very heavy cylinders cannot be transported in large numbers using trucks.
5. Hydrogen can be stored in liquid form. For that, the temperature must be very low. So the cylinders carrying the liquefied dihydrogen must be well insulated. Such tanks are very expensive.
6. Production of hydrogen is also an expensive process. We are having to burn large quantities of coal to produce sufficient quantities of hydrogen. This is not economical. Also, it contributes to environmental pollution.
7. Our present day society is powered by carbon. We burn carbon based fuels like coal, petrol diesel etc., to produce power to run our electrical appliances, automobiles and factories.
• If we can find ways for cheap production, storage and transportation of hydrogen, we can shift to a hydrogen economy. This will help to save our planet.
The link to some solved examples is given below:
We
have completed the discussions in this chapter. In the next chapter, we
will see s-block elements.
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