Non-metals

Preparing nitrogen (N₂) in laboratory:

Heating a mixture of sodium nitrite and ammonium chloride gives ammonium nitrite (NH₄NO₂) which is highly unstable.

NaNO₂ + NH₄Cl → NH₄NO₂ + NaCl

Ammonium chlorate readily decomposes to give nitrogen gas.

NH₄NO₂→ N₂ + 2H₂O

Preparing hydrogen (H₂) in the laboratory:

a) Zinc (Zn) when treated with sulphuric acid (H₂SO₄) liberates hydrogen gas.

Zn + H₂SO₄→ ZnSO₄ + H₂

b) Zinc when treated with hydrochloric acid (HCl) also liberates hydrogen gas.

Zn + 2HCl → ZnCl₂ + H₂

c) Water upon electrolysis gives hydrogen and oxygen. Electrolysis is the process of decomposition produced when an electric current is passed through a solution.

Hydrogen (H₂)

Water upon electrolysis gives hydrogen and oxygen.

Hydrogen is a combustible gas. That is it can catch fire or burn easily. Oxygen itself is not a combustible gas, but it supports combustion (it helps in burning of fuels).

Chlorine (Cl₂)

Chlorine acts as a disinfectant, and hence is added in a limited amount to water to kill certain microbes. If it is overly used, then it can cause health problems.

Nitrogen (N₂)

The rhizobium bacteria are present in the root nodules of leguminous plants (like pea plants). They convert the atmospheric nitrogen into nitrogen compounds (like ammonia). In this form, plants are able to absorb these compounds that help in their growth. This process of converting atmosphere N₂ into nitrogen compounds is called nitrogen fixation.

Oxygen (O₂)

Potassium permanganate (KMnO₄) is a strong oxidising agent and on heating gives potassium manganate (K₂MnO₄), manganese dioxide (MnO₂) and oxygen.

Hydrogen – Fuel

Hydrogen is a combustible gas and burns in the presence of air to produce high amounts of energy. Unlike traditional fuel sources (fossil fuels), it does not produce products that pollute the environment. It burns in the presence of oxygen to produce water and releases energy. It is widely used in fuel cells.

2H₂ + O₂→ 2H₂O + energy

Oxygen – biodegradation

Biodegradation is the process of disintegrating or breaking down of materials like remains of plants and animals by microorganisms like bacteria, fungi etc. This can happen in the presence or absence of oxygen. The process is called aerobic biodegradation, if it occurs in the presence of oxygen.

Chlorine – disinfectant

Chlorine is a very powerful disinfectant which deactivates/destroys harmful microorganisms present in drinking water, or water bodies. It can be easily applied, and is very cheap as well. It also prevents spread of contagious diseases up to an extent.

Nitrogen – refrigerant

Liquid nitrogen is used as a refrigerant. It is used to store substances at a very low temperature. This is widely used as coolants for computers, and also in cold storage units to store blood, body cells, etc. Nowadays, it has found applications in cooking as well.

The chemicals used for the preparation of chlorine are potassium permanganate (KMnO₄) and concentrated hydrochloric acid (HCl).

The reaction is as follows:

2KMnO₄ + 16HCl → 2KCl + 2MnCl₂ + 8H₂O + 5Cl₂

Concentrated sulphuric acid is a very effective drying agent. The chlorine obtained as the product from the above reaction contains traces of water vapour, and hydrogen chloride (HCl) vapours. HCl vapours are removed by passing the gas through water, and the traces of water vapour are removed by passing through conc. sulphuric acid.

Bleaching powder is prepared by passing chlorine gas over dry slaked lime (calcium hydroxide – Ca(OH)₂). The reaction involved is:

Ca(OH)₂ + Cl₂→ CaOCl₂ + H₂O

(bleaching powder)

Chlorine gas is liberated when bleaching powder reacts with water.

CaOCl₂ + H₂O → Ca(OH)₂ + Cl₂

Chlorine is responsible for the bleaching/disinfection action.

Before coming to a conclusion, let us look at the advantages and disadvantages of organic and chemical fertilisers.

Organic Fertilisers:

Chemical Fertilisers:

So, it would be better if one uses organic fertilisers as there is little to no risk involved when applying it to the soil. It may not be commercially productive for farmers in a large scale. Hence, people tend to use chemical fertilisers as they provide results in a smaller time scale.

Nitrogen cycle can be defined as the circulation of nitrogen in various forms in different aspects of the nature.

Various processes are involved in this cycle. The important processes are mentioned here briefly.

•The atmospheric nitrogen is converted to nitrogen compounds (for e.g., nitrates) by nitrogen fixation caused by lightning, and rhizobium bacteria.

•The oxides of nitrogen as a result of combustion of fuels, combine with water to form acids, which seeps into the ground, later forming nitrates.

•These compounds (nitrates, nitrites etc) can be consumed by plants for their growth.

•These plants are later consumed by animals, and they excrete nitrogenous wastes, which are converted to useful nitrates by nitrifying bacteria.

•The dead animals/plants also decompose to produce nitrogen content in the soil.

•Again, these nitrates are in a usable form for plants for their intake.

•The cycle is completed when the nitrogen compounds are denitrified into nitrogen gas.

Here, animals get sufficient amount of nitrogen by eating plants, and plants get sufficient amount of nitrogen from the soil as a result of nitrification, or decomposition of dead organic matter. Hence both parties are benefitted by the nitrogen cycle.

Ozone layer is the layer formed by ozone (O₃) and is found in the Earth’s stratosphere. This layer protects the earth from the ultraviolet (UV) radiation coming from the sun, by absorbing them.

The increased content of Chlorofluorocarbons (CFCs) arising from usage of aerosol sprays, and cleaning solvents caused a huge breakdown of ozone, resulting in ozone layer depletion.

This has resulted in UV radiation entering the atmosphere and caused a sudden increase in overall temperature, due to the trapping of the heat by greenhouse gases like carbon dioxide. This ultimately leads to “global warming”. This leads to the melting of polar ice caps, and other environmental issues. Humans on exposure to UV radiation can cause skin cancers as well.

To resolve the ozone layer depletion problem internationally, policies were introduced to minimise or avoid the usage of CFC included aerosol sprays, and refrigerants. On an individual basis, one could,

•plant more trees so that the increased amount of greenhouse gases are absorbed by the trees.

•usage of aerosol sprays or refrigerants that do not contain CFCs.

•replacing incandescent light bulbs with fluorescent lamps, as they are void of halogen content.

•limit the usage of private vehicles whenever necessary, so as to minimise the emission of greenhouse gases.

One can see that the dying flame gets “rejuvenated” or begins to burn properly (or one can say, the flame looks “live”).

Hydrogen peroxide (H₂O₂) by itself slowly decomposes into water and oxygen. When manganese dioxide (MnO₂) is added, the rate of decomposition is made faster, and O₂ is liberated at a faster rate. The oxygen supports the burning of match stick, and that is why one can see it burning effectively.

There is not any reaction involved, but the rate of decomposition of H₂O₂ is increased. Here, MnO₂ acts as a catalyst.