Question

Given below are two statements:
Statement (I): Humus is the amorphous material derived from the decomposition of organic matter.
Statement (II): Allophane is a crystallite mineral developed from volcanoes
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

Allophane and Imogolite are classic examples of "non-crystalline" or amorphous silicate clays found in volcanic soils (Andisols).
Remembering that they lack crystalline structure helps identify Statement II as incorrect.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Soil contains both organic colloidal fractions (such as humus) and inorganic mineral colloidal fractions (such as clay minerals).
These components are classified based on their structural order as crystalline (highly ordered) or amorphous (short-range ordered or non-crystalline).

Step 2: Detailed Explanation:
Let us analyze both statements:
- Statement (I): "Humus is the amorphous material derived from the decomposition of organic matter."
Humus is a complex, dark-colored, highly stable, and non-crystalline (amorphous) organic macromolecular mixture.
It is produced through the physical, chemical, and biological decomposition of plant and animal residues in the soil.
Thus, Statement (I) is true.
- Statement (II): "Allophane is a crystallite mineral developed from volcanoes."
Allophane is an aluminosilicate clay mineral commonly found in soils derived from volcanic ash (Andisols).
However, allophane is a non-crystalline (amorphous) or poorly ordered, short-range-order mineral.
It lacks the long-range repeating crystal lattice structure typical of crystalline silicate clays like kaolinite or montmorillonite.
Therefore, describing it as a "crystallite" (crystalline) mineral is incorrect.
Thus, Statement (II) is false.

Step 3: Final Answer:
Statement (I) is true but Statement (II) is false.