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Questions and Answers
What is the primary origin of Kieselguhr?
What is the primary origin of Kieselguhr?
- Mineral consisting of siliceous skeleton of fossil diatoms (correct)
- Chemical compound from CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub>
- Indefinite amorphous masses from chemical reactions
- Purified native hydrated Mg-trisilicate
Which shape is NOT associated with the valves of Kieselguhr?
Which shape is NOT associated with the valves of Kieselguhr?
- Oval discs
- Triangular discs
- Rounded discs
- Hexagonal discs (correct)
What is a notable feature of Talc when it is subjected to water?
What is a notable feature of Talc when it is subjected to water?
- It sinks to the bottom
- It releases gas bubbles
- It floats on the water surface (correct)
- It dissolves completely
Which of the following statements about chalk is true?
Which of the following statements about chalk is true?
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Which type of starch is characterized by a polygonal shape with sharp edges?
Which type of starch is characterized by a polygonal shape with sharp edges?
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What is the appearance of sulphur under microscopic examination?
What is the appearance of sulphur under microscopic examination?
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What reaction forms the heavy chalk?
What reaction forms the heavy chalk?
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What type of appearance do the valves of Kieselguhr exhibit?
What type of appearance do the valves of Kieselguhr exhibit?
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Study Notes
Kieselguhr
- Originates from fossilized diatoms, a type of algae.
- Diatoms have a unique structure: two overlapping shells called valves, which can be rounded, oval triangular, or pinnate (feather-like) in shape.
- Diatom valves exhibit intricate patterns like honeycombs or spongy spicules.
Talc
- A hydrated magnesium silicate, with minor amounts of alumina and iron oxide.
- Appears as thin plates with sharp, jagged edges.
- Floats on the surface of water.
Chalk
- Formed by the chemical reaction of calcium chloride (CaCl2) and sodium carbonate (Na2CO3).
- There are two types:
- Heavy Chalk: Larger crystals, rectangular with irregular shapes, found individually.
- Light Chalk: Composed of smaller crystals that clump together.
- Both types react with hydrochloric acid (HCl) to produce effervescence and carbon dioxide (CO2).
Sulfur
- Obtained through a chemical reaction involving calcium hydroxide (Ca(OH)2) and sublimed sulfur (S).
- Appears as irregular, amorphous masses with a shiny appearance in a dark background.
- Has a characteristic yellow color and a sulfur-like odor.
Starch
- Microscopical examination distinguishes different types of starch:
- Potato Starch: Oval, pyramidal shape.
- Wheat Starch: Rounded.
- Maize Starch: Polygonal with rounded edges.
- Rice Starch: Polygonal with sharp edges.
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