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Why do not lichens occur in Delhi wherea...

Why do not lichens occur in Delhi whereas they commonly grown in Manali or Darjeeling?

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### Step-by-Step Solution: 1. **Definition of Lichens**: Lichens are a symbiotic association between algae and fungi. They are unique organisms that can thrive in various environments. 2. **Role as Bio-indicators**: Lichens serve as bio-indicators of air quality. They are sensitive to air pollution, particularly to sulfur dioxide (SO2), which is a common pollutant. 3. **Pollution Levels in Delhi**: Delhi is known for its high levels of air pollution, primarily due to emissions from vehicles and industrial activities. The concentration of pollutants, especially sulfur dioxide, is significantly higher in Delhi compared to other regions. ...
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When an atom or an ion is missing from its normal lattice site, a lattice vacancy (Schottky detect) is created In stoichiometric ionic crystals, a vacancy of one ion has to be accompanied by the vacancy of the oppositely charged ion in order to maintain electrical neutrality. In a Frenkel defect an ion leaves its position in the lattice and occupies an interstitial void.This is the Frenkel defect commonly found along with the Schottky defects and interstitials.In pure alkali halides, Frendel defect are not found since the ions cannot get into the intenstitial sites.Frenkel defects are found in silver halides because of the small size of the Ag^+ ion.Unlike Schottky defects. Frenkel defects do not change the density of the solids.In certain ionic solids (e.g. AgBr) both Schottky and Frenkel defects occur. The defects discussed above do not disturb the stoichiometry of the crystalline meterial.There is large Such solids showing deviations from the ideal stoichiometric composition form an important group of solids For example in the vanadium oxide, VO_x , x can be anywhere between 0.6 and 1.3.There are solids which are difficult to prepare in the stoichiometric composition.Thus, the ideal composition in compounds such as FeO is difficult to obtain (normally we get a composition of Fe_(0.85) O but it may range from Fe_(0.93) O to Fe_(0.96)O ).Non-stoichiometric behaviour is most commonly found for transition metal compounds through is also known for some lanthanoids and actinodes. Zinc oxide loses oxygen reversibly at high temperature and turns yellow in colour.The excess metal is accomdated interstitially, giving rise to electrons trapped in the neighbourhood.the enhanced electrical conductivity of the non-stoichiometric ZnO arises from these electrons . Anion vacancies in alkali halides are produced by heating the alkali halide crystals in an atmosphere of the alkali metal vapour.When the metal atoms deposite on the surface they diffuse into the crystal and after ionisation the alkali metal ion occupies cationic vacancy whereas electron occupies anionic vacancy.Electrons trapped in anion vacancies are referred to as F-centres (from Farbe the German word for colour) that gives rise to interesting colour in alkali halides.Thus, the excess of potassium in KCl makes the crystal appear violet and the excess of lithium in LiCl makes it pink. In the crystal of Fe_(0.93)O , the percentage of Fe (II) will be

Carbon and silicon belong to group IV . The maximum coordination number of carbon in commonly occuring compounds is four whereas that of silicon is six. This is due to

Carbon and silicon belong to group IV . The maximum coordination number of carbon in commonly occuring compounds is four whereas that of silicon is six. This is due to

When an atom or an ion is missing from its normal lattice site, a lattice vacancy (Schottky defect) is created. In stoichimetric ionic crystals, a vacancy of one ion has to be accompanied by the vacancy of the oppositely charged ion in order to maintain electrical neutrality. In a Frenkel defect an ion leaves its position in the lattice and occupies an interstitial void. This is the Frenkel defect commonly found along with the Schottky defects and interstitials. In pure alkali halides, Frenkel defects are not found since the ions cannot get into the interstitial sites. Frenkel defects are found in silver halides because of the small size of the Ag^(+) ion. Unlike Schottky defects, Frenkel defects do not change the denstiy of the solids. In certain ionic solids (e.q. AgBr) both Schottky and Frenkel defects occur. The defects discussed above do not disturb the stoichiometry of the crystalline material. There is large variety of non-stoichiomertic inorganic solids which contain an excess or deficiency of one of the elements. Such solids showing deviations from the ideal stoichiometric composition from an inmportant group of solids. For example in the vanadium oxide, VO_(x) , x can be anywhere between 0.6 and 1.3. There are solids which are difficult to prepare in the stoichiometric composition. Thus, the ideal composition in compounds such as FeO is difficult to obtain (normally we get a composition of Fe_(0.95)O but it may range from Fe_(0.93)O " to " Fe_(0.96)O ). Non-stoichiometric behaviour is most commonly found for transition metal compounds though is also known for some lanthanoids and actinoids. Zinc oxide loses oxygen reversibly at high temperature and turns yellow in colour. The excess metal is accommodated interstitially, giving rise to electrons trapped in the neighbourhood. The enhanced electrical conductivity of the non-stoichiometric ZnO arises from these electrons.ltrbgt Anion vacancies in alkali halides are produced by heating the alkali halide crystals in an atmosphere of the alkali metal vapur. When the metal atoms deposit on the surface they diffuse into the crystal and after ionisation the alkali metal ion occupies cationic vacancy whereas electron occupies anionic vacancy. Electrons trapped in anion vacancies are referred to as F-centers (from Farbe the German word for colour) that given rise to interesting colour in alkali halides. Thus, the excess of potassium in KCl makes the crytal appear violet and the excess of lithium in LiCl makes it pink. When LiCl is heated into the vapour of lithium, the crystal acquires pink colour. This is due to

NCERT EXEMPLAR ENGLISH-NATURAL RESOURCES -Short Answer Type Questions
  1. Rivers from land, add minerals to sea water. Discuss how ?

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  2. How can we prevent the loss of top soil?

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  3. How is the life of organisms living in water affected when water gets ...

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  4. During summer, if you go near the lake, you feel relief from the heat,...

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  5. In coastal area, wind current moves from the sea towards the land duri...

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  6. Following are a few organisms Which among the above can grow on stone...

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  7. Soil formation is done by both abiotic factors. List the names of thes...

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  8. All the living organisms are basically made up of C,N,S,P,H and O, . H...

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  9. Why does the percentage of gases like oxygen, nitrogen and carbon diox...

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  10. Why does moon have very cold and very hot temperature variations e.g.,...

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  11. Why do people love to fly kites near the seashore ?

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  12. Why does Mathura refinery pose problems to the Taj Mahal?

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  13. Why do not lichens occur in Delhi whereas they commonly grown in Manal...

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  14. Why does water need conservation even though large oceans surround the...

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  15. There is mass mortality of fishes in a pond. What may be the reasons?

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  16. Lichens are called pioneer colonisers of bare rock. How can they help ...

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  17. Soil is formed by water'. If you agree to this statements then give re...

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  18. Fertile soil has lots of humus. Why?

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  19. Why step farming is common in hills?

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