Question

What is the average content of silica in soil.
(a)21%
(b)24%
(c)27%
(d)30%

Answer 1

Hint: Silica is silicon dioxide which has many importances in the commercial field. Its most common form ‘quartz’ makes up 10% of the earth's crust and in many parts of the world, it is found abundantly in the sand.

Complete answer:
Nearly 27% of silica is present in the soil.
Silica is an oxide of silicon that is found in nature as the major constituent of sand in many parts of the world and as quartz and also in various living organisms. It consists of 10% of the earth's crust. It is found in many Plants and is a primary component of rice husk ash.

Additional Information: Silica is one of the most complex and most abundant materials and found in many parts of the world as a major constituent of sand, like quartz, in many plants, rice husk ash, in single-cell organisms like bacteria, plants, and animals. Some examples of this include tests of diatoms, Radiolaria, silica phytoliths in many plants like Equisetaceae, and spicules of many sponges. Quartz is the most common form of silica found on the earth's surface and other metastable forms are coesite and stishovite. Some high-temperature forms are tridymite and cristobalite.
Uses:
-production of concrete
-sand casting of metallic products
-hydraulic fracturing of formations having tight oil and shale gas
-production of glass and silicon
-production of fumed silica that is used as pozzolanic material for high-performance concrete
-additive in food production
-useful in the production of cosmetic
-used as semiconductor, defoamer component, high-temperature thermal protection fabric, and as fused quartz.
So, the correct answer is "27%".

Note: Though Silica is an abundant and useful material, it has many harmful effects on humans. Its finely divided crystalline form is very toxic and when inhaled by a person may lead to severe inflammation of the tissues of lungs, silicosis, bronchitis, lung cancer, and systemic autoimmune diseases like lupus and rheumatoid arthritis. Another amorphous form of silica may cause non-permanent short term inflammation when inhaled in high doses.