Tag: chemistry

Deforestation, clearance or clearing is the removal of a forest or stand of trees where the land is thereafter converted to a non-forest use. The less the soil is covered with vegetation, mulches, crop residues, etc., the more the soil is exposed to the impact of raindrops. When a raindrop hits bare soil, the energy of the velocity detaches individual soil particles from soil clods. Thus Deforestation would decrease the water holding capacity of the soil, so statement is false and Option B is correct.

Underground soil in cities is likely to be polluted by Chemicals released by industrial wastes and industrial wastes Decomposed and partially decomposed materials of sanitary wastes Many dangerous chemicals like cadmium, chromium, lead, arsenic, selenium  products are likely to be deposited in underground soil. Similarly underground soil polluted by sanitary wastes generate many harmful chemicals.These can damage the normal activities and ecological balance in the underground soil.

$As$ is a member of group $V$ and has 5 electrons in its outermost shell. 

An n-type semiconductor is due to the presence of a free electron in the semiconductor. Since silicon is an element having $4$ valence electrons, in order to have a free electron, it must be doped with an element having one more valence electron than silicon. 

In semiconductor two types of the semiconductor are present. They are an intrinsic and extrinsic semiconductor. A pure silicon crystal is an example of an intrinsic semiconductor. 

To form a p-type semiconductor, one must add elements from boron family to the silicon atom.