Chemistry
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New answer posted
11 months agoContributor-Level 10
The amount of oxygen required by bacteria to breakdown the organic matter present in a certain volume of a sample of water is called Biochemical Oxygen Demand (BOD).
New answer posted
11 months agoContributor-Level 10
Yes, we observed water pollution near our area due to various human activities like toxic discharges from factories and industrial plants, runoff from agricultural fields, domestic wastes etc.
It can be controlled by preventing the toxic chemicals from entering the water bodies. Regular checks on contamination or rivers, lakes or ponds of toxic compounds need to be done. Use of chemical fertilizers should be avoided to prevent the harmful chemicals from entering the ground water.
New answer posted
11 months agoContributor-Level 10
Major Causes of water pollution are:
Pathogens: Pathogens include bacteria and other microorganisms that enter water from domestic sewage and animal excreta.
Human excreta contain bacteria such as Escherichia coli and Streptococcus faecalis, which cause gastrointestinal diseases.
Organic wastes: Organic wastes, when added to water, are decomposed by bacteria, which consume dissolved oxygen in water. When the concentration of dissolved oxygen in water decreases below 6 ppm, the growth of fish is inhibited. The breakdown of organic wastes by anaerobic bacteria produces chemicals that have a foul smell and are harmful to human health.
Ch
New answer posted
11 months agoContributor-Level 10
1.27 The different solids are classified below:
a) Ionic solids: Ammonium phosphate (NH4)3PO4), LiBr
b) Metallic solid: Brass, Rb
c) Molecular solids: Tetraphosphorous decaoxide (P4O10), Iodine (I2), P4
d) Network (covalent) solids: Graphite, SiC, Si
e) Amorphous solid: Plastics
New answer posted
11 months agoContributor-Level 10
Depletion of ozone layer creates some sort of holes in the blanket of ozone which surrounds us, this is known as ozone hole.
The consequences are:
- With the depletion of ozone layer, more UV radiation filters into troposphere. UV radiations lead to ageing of skin, cataract, sunburn, skin cancer, killing of many phytoplanktons, damage to fish productivity etc.
- It has also been reported that plant proteins get easily affected by UV radiations which leads to the harmful mutation of cells.
- It also increases evaporation of surface water through the stomata of the leaves and decreases the moisture content of the soil.
4. Increa
New answer posted
11 months agoContributor-Level 10
3.30. (i) For n = 3, the element belong to 3rd period, p-block element.
The electronic configuration is =1s2 2s2 2p6 3s2 3p4. The element name is sulphur.
(ii) For n = 4, the element belongs to 4th period and since the valence shell has 4 electrons it belongs to group 4.
Electronic configuration= 1s2 2s2 2p6 3s2 3p6 3d2 4s2, and the element name is Titanium (Ti).
(iii) For n = 6, the element belongs to 6th period. Last electron goes to the f-orbital, element is from f-block. It belongs to group = 3
The element is gadolinium (z = 64)
Complete electronic configuration = [Xe] 4 f7 5
New answer posted
11 months agoContributor-Level 10
3.29. (i) s-Block elements: ns1-2 where n = 2-7.
(ii) p-Block elements: ns2 np1-6 where n = 2-6.
(iii) d-Block elements: (n-1)d1-10 ns 0-2 where n = 4-7.
(iv) f-Block elements: (n-2)f0-14 (n-1)d0-1 ns2where n = 6-7.
New answer posted
11 months agoContributor-Level 10
1.26 Quartzis crystalline solid with long range order and glass is amorphous solid (or pseudo solid or super cooled liquid) with short range order and has a tendency to flow. When quartzis heated, it can be converted into glass.
New answer posted
11 months agoContributor-Level 10
1.25 Amorphous solids have short-range order with irregular shapes of constituent particles. They have isotropic nature and melt over a range of temperatures. They do not have a definite enthalpy of fusion. Examples of amorphous solids are glass, rubber, plastic, etc.
New answer posted
11 months agoContributor-Level 10
3.28. The elements of Group I have only one electron in their respective valence shells and thus have a strong tendency to lose this electron. The tendency to lose electrons in turn, depends upon the ionization enthalpy. Since the ionization enthalpy decreases down the group therefore, the reactivity of group 1 elements increases in the order Li < Na < K < Rb < Cs. In contrast, the elements of group 17 have seven electrons in their respective valence shells and thus have strong tendency to accept one more electron to make stable configuration. So for group 17, the electron gain enthalpy and electronegativity decreases down the group and thus the reactivity also decreases.
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